Changes

Cleanup for PermissionUtil and fixed user_limit check. (#324)
* Cleanup for PermissionUtil and fixed user_limit check.
* Fixed a bug in ChannelUpdateHandler that removed all overrides (wrong
id)
 (commit: 319aae5)

MessagePaginationAction and some adjustments to MessageHistory (#343)
* Added MessagePaginationAction and made some adjustments to
MessageHistory for "efficiency"
* Removed exception printing for removeShutdownHook to prevent
IllegalStateException on shutdown by removing hook while jvm shutdown in
process
* Make PaginationAction entity cache opt-out
* Made new PaginationIterator implementation start off with already
cached entities
 (commit: fc0bc56)