[MCOMPILER-544] don't add items to classpath that are not used for that

[laeubi]

Currently simply all kind of items are added to the classpath leading to strange errors in the ECJ compiler plugin because it does not know how to handle pom or other possible types.

This adds an additional check to see if the artifact handler actually claims the itme should be put on the classpath,

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[gnodet]

LGTM

[slawekjaranowski]

Cen we add example from jira as IT?

[laeubi]

Cen we add example from jira as IT?

I'm not that familiar with compiler-itests but it should be enough to check that no ERROR printout is there when executing the given pom example on a project that has at least one dummy source file so compilation is triggered...

[laeubi]

@slawekjaranowski can you help with the test-case here? I anything else needed or does it look sane?