xinput-calibrator: move it from meta-oe to oe-core
People using xserver-xorg that need to calibrate their touchscreen
devices would also need meta-oe. Bringing the recipes to oe-core will
make it easier for them.
Aditionaly:
* drop xterm RDEPENDS. Terminal is not needed to run the menu item;
* change xinput_calibrator_pointercal.sh so that it can be run as
normal user: pointercal.xinput is saved to ~/.pointercal/ and it will
be used when the system boots;
* have the calibration run through an Xsession file;
* remove the systemd service since calibration is run by Xsession;
* do not install pointercal.xinput if it's the default one;
