Externalize common part.
Remove old userguide folder.
Update distro ant file.

Docs cleanup + adding documentation for new Async Executor architecture + Message queue based Async Executor.

Update of joda-time library (from 2.1 to 2.6) to support timezone changes in some countries, e.g. in Russia.

Update of joda-time library (from 2.1 to 2.6) to support timezone changes in some countries, e.g. in Russia.