Updated to XStream 1.4.7

Notes:
- Using Apache servicemix bundle instead of the original XStream
  bundle because it does not require the 'sun.misc' import. Creating
  an extension framework bundle is too much fuss.
- Starting with 1.4.x, the OmitField annotation behaves differently:
  it also prevents reading the field which is needed to migrate the
  deprecated field.
Load XML file in background thread instead of UI thread
Update progress monitor when reading from file input stream
Added AES 256 encryption if file name ends with .portfolio
Simplified model upgrade code
Updated build dependencies (tycho, p2 orbit)