Player Control Improved, Base Mechanics Complete

Added accel/deccel to player, as well as seperate customiseable values
for a whole host of things that define the feel of the player, including
ground/air drag, max movement speed, gravity coefficient, jump strength,
etc.

These values are loaded in from a config XML file located in
ConfigFiles/PlayerConfig.xml, the designers can fiddle with these values
till there hearts content. If the file isnt found code based defaults
are used, defined in Player.cpp - LoadConfigValues()

Also locked the simulation rate to 60fps with a deltaTime accumulator
based approach, it dosent interpolate between frames, (although this may
have to be implemented later, at least for the player.) Rendering and
simulation are technically uncoupled, but rendering dosent do any
smoothing so it's pointless, at least the game is completely framerate
independent now, for both linear motion and acceleration.