experimentally add package import versions to bundles

Merged bundles not yet supported.
support different import version strategies
package import versions for merged bundles
deal with multiple occurrences of a single package in dependencies
sort import package instructions

...so correct handling is assured. If the packages were not sorted (longer names
coming first) due to the wild cards wrong versions could be applied.
ignore certain packages seemingly provided by Jars
added new platformaux configuration

platformaux ensures that the dependencies added there are added as additional bundles
to the platform. It allows adding multiple versions of the same dependency, but it
(at least currently) ignores transitive dependencies.
support dependency specific imports configuration
allow versionStrategy returning null
make the MAJOR version strategy the default
support overriding the bnd configuration for all bundles
strip artifact symbolic names of directives
added prependImport to BndConfig, more robust implementation
optionalImport/prependImport retain attributes of other packages
don't wrap existing source bundle files

Otherwise the override configuration could apply and add package exports,
which is most undesirable for source bundles!
removed debugging output
retain Bundle-SymbolicName attributes
automtatic package import versions disabled by default
implemented qualifiers based on bnd configuration hash

This helps circumventing caching issues when changing bundle configurations,
e.g. in Eclipse or Maven Tycho when resolving an Update Site, where the updated
configuration may not be avaialble due to a cached bundle being used.
The changed version should help with that.
added option to adapt symbolic names in platformaux

if auxVersionedSymbolicNames is set to true, all bundles created
in platformaux will have adapted bundle symbolic names that include
the module version.