Added CVAR 'sharptimer_enable' to enable/disable plugin functionality

[madelinelily]

fix for: #99

wrote up a cvar to allow for enabling/disabling the plugin without restarting the server.

sharptimer_enable 1 or true in any variant for enabling
sharptimer_enable 0 or false in any variant for disabling
no args will print current status
any other args will do nothing

list of tests run:

known bugs:
-feet contact shadows sometimes remain after re-enabling plugin
-ad text still prints
-an error on disconnect

also: ranks showing/hiding doesn't quite work right at the moment, but that should be fixed here: #98

will make changes for ^^ if necessary after the other PR is in

[rcnoob]

unfortunately i'm not quite sure adding +239 lines of code to solve one issue with one server is the best way to get your server fixed up. personally if I were in your shoes, I would just fork the dev branch, insert your mods, then compile and run a custom version

[madelinelily]

we wanted to get this out there on the off chance that someone else would need this functionality as well, on top of not having to manually update every time this plugin has changes. i understand, though.