Rebuild manifest when bnd instructions change in the pom (or in included bnd files)

[ifedorenko]

Originally opened as https://bugs.eclipse.org/bugs/show_bug.cgi?id=360875

Currently when you edit bnd instructions inside the pom.xml of a project with
bundle packaging you get an error marker telling you the Maven project
configuration is out-of-date and needs an update. It would be useful if instead
it could regenerate the manifest with the new instructions.

Some bundle projects also include external bnd files using
<_include>something.bnd</_include> (these files may themselves include other
bnd files). So we might also want to consider regenerating the manifest when
any included bnd files change.

[ifedorenko]

Updated m2e-tycho to rebuild manifest both when m-b-p pom.xml configuration changes and/or when any of included bnd files change.

Only immediately included bnd files trigger manifest regeneration, which, as discussed offline, should cover majority of real-world projects.

Change of generated bundle manifest in m-b-p configuration results "updated project configuration" error marker. For all other m-b-p configuration changes m2e-tycho simply regenerates bundle manifest.