migrate from directly invoking p2 functions to letting PDE/Build do that
- enable "p2.gathering"
- remove manually creating a local update site
- for now don't use manual "generateMetadata"
- split updateSiteTests into {eclipse,otdt}
  - otdt part is filled by PDE/Build instead of unpacking a generated zip

consume Orbit's bcel via map file instead of manual copying around
- no longer copy into dropins but rely on PDE/Build
  - installing it into eclipse/plugins
  - gathering it to the local repository

Pending:
- re-establish re-use of metadata from previous build
  (check skipMirroring)
- additional assemble.XX targets in customTargets could be avoided by
  migrating to more modern customTargets / allElements

6 files changed