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

Define a 'plugin' function to use in place of 'project' that
will figure out where the plugin is living in the root gradle
project.

This allows the plugins to be included and built properly
when they are in a submodule of either the client or the meta
project.

Change-Id: Iacc3551ac9c0bf2343151eb9cf85296c85c5a28b
Reviewed-on: http://gerrit.dmdirc.com/4028
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

Change-Id: I7a0866b87c71e8251aa5cba5fd227fe7dbed941e
Reviewed-on: http://gerrit.dmdirc.com/4014
Reviewed-by: Chris Smith <chris@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

Feel like we've got a few too many moving parts at the moment,
so explicitly set versions of our dependencies.

Also took the opportunity to upgrade a couple of things.

Change-Id: I1af4dbfbbd149e5a4c64e83f66de015affcf4032
Reviewed-on: http://gerrit.dmdirc.com/4001
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

* 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>