Fix servlet version
AS7-6868 - Introduce IO subsystem

this is split from undertow subsystem so xnio configuration & friends can be all in same place for everyone to use
Fix defaults for workers
get rid of servlet 2.5 dependency
[AS7-6244] Add support for bundles refresh
[JBOSGI-642] Consolidate attachments API
[AS7-6879] LockContext not propagated across management boundary