Is a computational scientist/engineer a viable professional goal? One one hand, there were attempts to give some meaning to the term on Wikipedia; there is a page on SIAM's website and a Master's program at Stanford.

On the other hand, there are very few jobs which use the term. However, there are positions with "Computational" and "Engineer" like "Computational Imaging Engineer", "Computational Biology Engineer" and so on.

I assume that skills and knowledge, which are necessary for doing a job with "Computational" in the name are, roughly, the same. Consequently, if a person has a core set of skills and knowledge, it should be easy to apply them in different fields.

Am I right in my assumption, and "computational scientist" is a possible career goal? Or it is too broad a term (e.g., a synonym for "applied mathematician") and should not be considered as a specific goal.
Computational science is more of a mode of work than an actual career path—using modeling and mathematical techniques to solve problems in engineering, medicine, finance, and other disciplines. Almost all computational scientists have an area of emphasis within that field (as you mentioned, computational imaging engineer or computational biologist). You can move within areas relatively closely related, but making larger leaps may be more difficult: a computational fluid mechanics expert cannot quickly be substituted for someone working in bioinformatics, and vice versa.