Previously I renamed the source assemblies from the uniform name
'sources' to something more individual like 'aspectjtools-sources', not
realising that the magic name 'sources' in combination with the default
configuration value 'appendAssemblyId=true' results in an artifact
classifier equal to the assembly ID, i.e. 'sources', which is exactly
what we need here, but not quite obvious. Therefore, I documented it
with comments in both the assemblies and the POMs.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

This is one step to get rid of org.aspectj:org.eclipse.jdt.core and
org.aspectj:asm-renamed in the 'lib' directory.

AspectJ tools + weaver uber JAR builds now use dependencies in the POM
in order to deal with creating binary + source assemblies. They no
longer rely on manually updated copies under 'lib'. Details:
  - Binaries are copied via 'dependencySets' in the assembly descriptor.
  - Sources are unzipped via Maven Dependency Plugin before including
    them into the source uber JAR via assembly descriptor.
  - NEW: This also includes ASM-renamed sources which so far were
    ignored. It is a positive side-effect from the fact that for
    ASM-renamed Maven Shade automatically creates a source JAR.
  - Maven Ant Run is no longer used for unzipping binary + source JARs.
  - While working in parallel with JDT Core and AspectJ it is now much
    easier to produce up to date artifacts, e.g. for consumption by
    AJDT, because it does not matter anymore if we forget to run the
    build in module 'lib' in order to update the JDT Core copy.

Status quo:
  - Folder lib/asm is no longer used and will be removed in a subsequent
    commit.
  - Folder lib/jdtcore-aj is no longer used by the Maven build, but
    still referenced in a few UNIX shell scripts and Ant build files.
    TODO: Find out if those are still actively used. If yes, refactor
    them to look for the file in the local Mavven repository. Otherwise,
    delete the referencing files and also lib/jdtcore-aj.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>