Add UI for installing mmo* plugins

[Rycochet]

Needs to get the plugin list from mmo.rycochet.net - will have to do a webpage for it later, currently I need to manually edit the versions.txt file.

Needs to understand requirements of plugins, so only offer to install plugins that can be run (ie, mmoInfoCoords needs mmoInfo too).

Needs to be able to manually update plugins - including unload/reload for them individually.

Layout would be something like -

[Install] mmoClass v0.1 - Description text
[Delete] [Update] [Edit] mmoBlah v1.1 - Description for an installed plugin

Any button press would ask for confirmation. The "Edit" button would let you edit the config values for that plugin.

Maybe borrow a page from Jenkins and have tabs - one for Updates, one for Installed plugins, and one for Available plugins...