ENH: Plugin Improvements (see wiki : http://www.paraview.org/ParaView3/index.php/Plugin_Improvements). Mainly: Better plugin name and version support; Maintain a list of autoload plugins that specified by user from UI, which will be loaded automatically; Better error reporting with visual hints on UI; Added "Required_on_server, Required_on_Client, Required_plugins" as optional argments to cmake macro ADD_PARAIEW_PLUGIN as mechanism to specify dependencies with server/client-side components and other plugins; Move plugin management to ServerManager layer so that python can access it as well.