Bug 1443: Added support for Union type & OSGI Runtime

Introduced new marker interface SchemaUnawareCodec
which marks codecs for simple value types,
which are unaffected by introduction of new modules
(practically everything except union, instance identifier
 and identity codecs). Reworked caching to cache only these
codecs.

Added integration with OSGI, which ensures proper class loading
and updates Javassist classpool if necessary.

Updated ModuleContext to not populate type to schema fields
with empty augmentations, which are undetectable in
data tree.

Change-Id: I2a2c8477e9fdc2ef53bd9f81956023c0760d620e
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>