Update XboxCtrlrInput.cs

Added GetDPadDown and GetDPadUp for Both All and Targeted Controllers.
Update XboxCtrlrInput.cs

Updated GetDPadDown and GetDPadUp to return false for all Linux Wired, until a supported update to this can be created.
Update XboxCtrlrInput.cs
Merge pull request #11 from ProjectEnder/master

Merge XboxCtrlrInput.cs from ProjectEnder. Adds GetDPadUp() and GetDPadDown(), but not Linux-ready.