Change OSGi start levels to accommodate workspace logic in .core bundle

- Set OSGi active start level in VM arguments in run config to 7
(-Dosgi.startLevel=7)
- Set start levels for pepper framework bundle to 7
- Set start levels for pepper import bundles to 6
- Set start level for .workspace bundle to default (leave auto-start to
true)
Set OSGi start levels in product to be the same as in run config
Remove refs to .workspace plug-in
Revert "Remove refs to .workspace plug-in"

This reverts commit 74c9abd8579f4ce80dfdbe546f3f7d836e6e0546.
Remove workspace plug-in and move code to .core
Clean up and refactor workspace-related code