Issue 407: Support for felix framework

This patch adds basic felix support. With these changes flyway can be used as library that is wrapped by an OSGi bundel (It is still not possible to deploy flyways as an OSGi bundle in felix). 

Since the fix only uses official OSGi interfaces/classes this fix should work for any OSGi container (I only tested the fix for felix though).

Behaviour in an Equniox environment is not changed by this patch.