JAXB extension cannot handle empty lines in jaxb.index
**Describe the bug**
I'm tweaking a Camel extension so that it makes use of the JAXB extension capability to discover classes from `jaxb.index`.

Here's the content of `jaxb.index` that is causing problems:

```
#
# Copyright 2005-2019 Dozer Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

AllowedExceptionsDefinition
ClassDefinition
ConfigurationDefinition
ConverterTypeDefinition
CopyByReferencesDefinition
```

The whitespace after the license header results in:

```
 Build step io.quarkus.jaxb.deployment.JaxbProcessor#process threw an exception: java.lang.RuntimeException: java.lang.ClassNotFoundException: com.github.dozermapper.core.builder.model.jaxb.
	at io.quarkus.jaxb.deployment.JaxbProcessor.handleJaxbFile(JaxbProcessor.java:232)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1553)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at io.quarkus.jaxb.deployment.JaxbProcessor.process(JaxbProcessor.java:207)
```


**Expected behavior**
The JAXB extension ignores empty lines in `jaxb.index` and continues to process the file.

**Actual behavior**
See CNFE stack trace above.

**To Reproduce**
Steps to reproduce the behavior:
1. Create a project with a `jaxb.index` file like the one above
2. Include the `quarkus-jaxb` dependency in the project
3. Observe aforementioned CNFE

**Environment (please complete the following information):**
 - Quarkus version: 1.0.1.Final

diff --git a/extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java b/extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java
index 722aeb05b54..d8f62b43e8b 100644
--- a/extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java
+++ b/extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java
@@ -218,8 +218,9 @@ private void handleJaxbFile(Path p) {
             addResource(path);
 
             for (String line : Files.readAllLines(p)) {
-                if (!line.startsWith("#")) {
-                    String clazz = pkg + line.trim();
+                line = line.trim();
+                if (!line.isEmpty() && !line.startsWith("#")) {
+                    String clazz = pkg + line;
                     Class<?> cl = Class.forName(clazz);
 
                     while (cl != Object.class) {
['extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java']