Remove native support for ancient chat and permissions plugins

[leonardo-dgs]

I didn't removed some plugins of which the last release is relatively recent.
I know that now, plugins should implement on their own Vault support, but tell me if I should delete them.

Here are the latest releases of chat and permissions plugins.

OverPermissions: Feb 20, 2014
DroxPerms: Aug 24, 2013
Permissions: N/A
Privileges: Aug 10, 2013
TotalPermissions: N/A
iChat: Jun 4, 2016
MChat: May 14, 2013
MChatSuite: Jul 10, 2012
rscPermissions: Aug 5, 2016
KPerms: Mar 5, 2014
PermissionsBukkit: Mar 2, 2016
SimplyPerms: May 30, 2012
Starburst: N/A
Xperms: Jul 3, 2013
bPermissions v2.0.9a: Dec 13, 2011
CommandsEx: May 4, 2013