Offline operations: Move compaction functionality from tablets servers to manager

[keith-turner]

In order to support compactions of tablets that are not hosted and keep the code simple there should be one compaction process for tablets that are hosted and unhosted. To accomplish this, all compaction functionality should be moved out of the tablet servers.

[keith-turner]

Document about moving compactions to the manager :

https://cwiki.apache.org/confluence/display/ACCUMULO/Moving+compactions+to+the+manager

[keith-turner]

This is done except for #3526 which has an issue.