Calibration data saving in /etc/psmoveapi on Linux

Calibration is saved in /etc/psmoveapi for root user on Linux.
Non-root users read calibration first from local ~/.psmoveapi
directory and then from /etc/psmoveapi if there is no local
calibration data.
Daemon mode for psmovepair

Psmovepair can be run as daemon monitoring for controller
connections via USB and automatically performing pairing procedure.
Removed unnecessary ifdefs
Fixed according to review comments.

Used effective uid instead of real uid to detect root user.
Used snprintf instead of stecpy+strcat+strcat in
psmove_util_get_system_file_path()
Merge pull request #101 from MooseTheBrown/automatic_pair

Automatic pair