Version bump (2.0.5 -> 2.1a)
Fix image preview making window show scrollbars
Change PluginManager for better support

- Add some simple error handling (logging to console)
- Add onEnable and onDisable events for the plugin to do things at
  start and end
- Add access to simple per-plugin "global" values that are defined in
  the plugin
Change Image Preview plugin to use new PluginManager features
Fix some bugs with clickable player names

- Change the CSS to make them glow when hoevered over instead of being
  underlined
- Fix the RegExp to find all usernames at the beginning of a normal
  chat line (including whispers)
Add link to new server-provided chat.css styling