[libupnp] fix null pointer deref
[DB] Changesets framework
[DB] implement changeset functionality for sqlite
[DB] implement changeset functionality for MySQL
[DB] make some video tables changelogged
[DB] make some music tables changelogged
remove: disable caching for browse results
[libUPnP] Split InvokeAction() so we can get access to the worker thread (TODO: might not be needed)
[libupnp] Sync Policy data structure
[libUPnP] SyncStatus Data structure
[libUPnP] 'SyncData' data structures
[libUPnP] add Changelog data structures
[libUPnP] add sync pair data structure
[libUPnP] helper that deal with sync status variables
[libUPnP] Add xml content sync service description
[libUPnP] add sync service specific didl extensions
[libUPnP] Content Sync skeleton
[UPnP] Add DB that keeps track of our sync relationships
[UPnP/DB] Add SyncPair tables and management
[UPnP] hookup content sync stuff to gui (TODO: remove, and unify with montellesses workgit add -p)