Adds the sdl implementation for all used PlatformWindowManager monitor functions. [This unit test](https://github.com/GarageGames/Torque3D/blob/development/Engine/source/windowManager/test/windowManagerTest.cpp#L28) will now pass for the SDL platform. Here is the equivalent in TorqueScript to test the functions via the Canvas object:```//Canvas.listDisplays();
function Canvas::listDisplays(%this)
{
%count = %this.getMonitorCount();
echo(%count SPC "monitor(s) detected.");
for (%i = 0; %i < %count; %i++)
{
echo("Monitor #" @ (%i + 1) SPC %this.getMonitorName(%i) @ ": " @ %this.getMonitorRect(%i));
}
}```
