In preparation for child eventbusses being removed, anything
trying to subscribe to specific windows now needs an explicit
check.

In the process, fixed two issues:

- channel who plugin was sending way too many requests - each
  connection was querying every channel in the client. i.e.,
  with 5 servers open there'd be 5 WHOs per channel...

- ServerFrame stops itself listening when *any* frame is closed.
  So closing a channel window then reconnecting wouldn't offer
  an SSL dialog, because it's already unbound the listener.

Issue DMDirc/DMDirc#662

* Move all plugins to their own top-level directories.
* Move resources out of source trees
* Add Gradle build scripts.
* Remove ivy and ant build scripts.

Change-Id: Ib69a48ef26800c174ccf51c84ff9d1f73529460f
Depends-On: I303b6b69518468f98d48d835b8f40135d9e4bcbf
Reviewed-on: http://gerrit.dmdirc.com/3850
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

Change-Id: I505dd85becbfe5e5fd611a69cee7678d84fb249f
Reviewed-on: http://gerrit.dmdirc.com/3775
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

Change-Id: I4e9a1bff765c0bd62caf284a028932cd8461632c
Reviewed-on: http://gerrit.dmdirc.com/3772
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>

Change-Id: I2cf35d5859c85c3609002f126241536fda5d588e
Depends-On: I2baa7e986ded54930093768238ed24cab8cf4bf7
Reviewed-on: http://gerrit.dmdirc.com/3770
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>

Change-Id: I166452c8596b841ad6c72c11f215fa3a085f8d0d
Depends-On: Ib12542d236757d76540d57ff54341e3b73ceb598
Reviewed-on: http://gerrit.dmdirc.com/3438
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>

Change-Id: Iddd0d935753c8f9ac45e540e876fec9a0e6a31d0
Reviewed-on: http://gerrit.dmdirc.com/3197
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>