Hard waves & new Mods

It took a while, but finally I've added waves 61-80 to the game. With this, hard mode should be properly playable.

Wave 80 also comes with a proper boss, in the form of the Great Sage... That one has slightly too many abilities, it's cheap is what it is.

The balancing is still a bit questionable, let me know what you think...

New mods have also been added corresponding to the 9 Avarage maps.

Standouts are the manual targeting override, changing a towers aiming to always shoot at the mouse, and the Fourth wall, letting units move through the tower.

Also did some minor tweaks to level-up messages, they should be less annoying early on now :)

And lastly and most importantly, renamed Extreme difficulty to Hextreme... It was right there all along xD

Have fun!