Restrict Import-Package for scala.*

Restrict the Import-Package OSGi manifest entry to match only binary compatible scala.* packages. This is necessary, because the Scala OSGi versions do not match the OSGi semantic versioning policy and are not binary compatible between their OSGi minor versions. This means that e.g. the scala-compiler-2.11 bundle will never work if it imports a scala.* package from 2.10 or 2.12. Thus this patch enforces a tight version range, only accepting versions within the same minor version. E.g. Applied to version 2.11.1 the range would expand to "[2.11,2.12)".

Additionally, a Java 6 execution environment will be enforced for OSGi.

All module bundles need to have their own version numbers. This was not the case before this commit. Although these module bundles were only build for testing, they are needed to be correct, now, that we have stricter package import constraints and some test cases rely on them.
Add JavaSE-1.7 to set of required execution environments.

Without it, Equinox on Java 7 might spit out some warnings, which might lead to the wrong impression, that the Scala bundles are not well supported for newer platforms.
Refined package imports for scala modules.

Made scala.xml.* import optional and removed scala.util.parsing.json import.
Re-added the scala.util.parsing package import, with optional resolution.
Merge pull request #3735 from lefou/osgi-fix

OSGi: Restrict Import-Package for scala.*