Generic LSP server support

Currently, all our LSPs are coded (mostly by copy/paste) of another LSP plugin that subclasses various IdeLsp* objects.

This is done, currently, because we don't have a generic way to implement LSPs. And we don't have that primarily because we use, heavily, libpeas to do the plugin loading. It is meant to handle various loading in such a way that we get a PeasPluginInfo associated with each (and only one) subclass for that plugin.

We might be able to work around this by creating our own plugin loader for peas that would allow us to mostly drop in a .plugin file for the various LSPs and perhaps enough information to discover where to find the configuration object.