Plugin Manager install logic

Added a field to tell ezRPG if a module has any further install logic to
be run. For instance, modules may need to do their own db calls, or want
to run certain functions before they're are fully activated, this field
will tell the system to go to the external install process after being
added to the system.
Also I fixed the delete function to remove hooks during uninstall.
Added a isModuleActive function to index.php

We should be checking if the module is active/valid prior to executing
so that we don't get stuck with a blank page.
Also i created our first reserved action for modules "Install" which
will coincide with e885bfe commit.
Added SiteURL setting to Installer

Needed a SiteURL setting for a few plugin features.
Added to func.modules.php for more functions.