Core: add time to all APIs. Declare MessageProcessor method as abstract.
LogPlugin: empty implementation.
Implemented WtfPlugin. Close #92.
Merge pull request #152 from rexim/wtf

Implemented WtfPlugin
WtfPlugin: proper handling of empty entries. Close #155.
WtfPlugin: case-insensitive selection of words from the DB. Close #153
Merge pull request #156 from rexim/wtf-bugfixes

WtfPlugin bugfixes
LogPlugin: start DAO implementation.
LogPlugin: enable plugin in Core.
LogPlugin: implement message saving. Small refactoring.
LogPlugin: enable log saving.
Merge branch 'origin/logging'. Close #4.
RoomProcessor: migrate to time-based API.
PersistentStore: plugins are now versioned independently. Close #141.
Migration: update script documentation.