Maintenance icon and API fixes

Changed the loading of the maintenance icon to be more predictable - It will load directly on startup and can now reloaded by using the "/maintenance reload" command as well.
Changed the reload message to read the proper changes.
API fix.

MySQL and some general bugfixes

Added "/maintenance setmotd <1/2> " command to edit the maintenance mode motd via a command
The Bungee version of the plugin will now automatically create a MySQL table if it is enabled, so you won't have to manually create one anymore
Fixed the ServerListPlus motd only changing on using the command, but not on the server startup
Fixed an error with canceling the start-/endtimer in the Bungee version
Fixed an error with removing players from the whitelist in the Spigot version
Fixed some other minor bugs
Some internal code cleanup

Great update for Spigot version + bugfixes and performance improvements

If you have ProtocolLib installed, you can set a custom server icon while maintenance is enabled, also the playercount-message and the playercount-hover-message are now available (as it has already been in the Bungee version)!
The Spigot version should be much more compatible with other motd-changing plugins, such as SexyMotd!
In the BungeeCord version of the plugin, the "/maintenance remove " command now also works for offline players
Fixed some other issues with the ProtocolLib integration
Minor textfix for the updatemessage in the Spigot version
General performance improvements

Code cleanup + bugfixes

Massive code cleanup for both the Bungee and Spigot version of the plugin
Minor performance improvements
Fixed start- and endtimers not being cancelled properly
Fixed an error for the "/maintenance update" command in the Spigot version
Fixed an error regarding the ServerListPlus integration in the Spigot version