Particle effects, audio fix, stamina system

Today I added a fun little particle system that displays when a teleport node is activated, along with a label that displays the name of the teleport while holding down the "alt" key. A shader also draws an outline around the teleport node while holding "alt".

Players now use a stamina resource when roll dodging, which regenerates over time. A bar graph at the bottom of the screen shows how much is remaining. You can manage about 3 rolls before using it all up.

I fixed a potential audio bug when activating teleport nodes, though I'm not sure if my builds were actually affected by it or not. I had noticed it on Windows while launching the game from the engine editor with version 4.2, but my recent builds have been from version 4.2.1, which supposedly has a fix for this issue. I changed the sound in question from WAV to OGG, and that did seem to fix it.

There is still a known issue where the background music isn't looping properly on Windows. As this is handled completely by the engine itself, I'll have to wait for a fix in the next minor release or start digging into the engine source code myself to fix it.

I'll probably take the next few days off, due to a work trip, so I tried to cram in as much as I could today.