Changed EPSxMODEL parameters to POLARx_MODEL.
Added AMODEL, BMODEL, THETAMODEL for both _IMAGE and _WORLD coordinates.
Added CXXMODEL CYYMODEL, CXYMODEL for both _IMAGE and _WORLD coordinates.
AddedTHETAMODEL_SKY,THETAMODEL_J2000,THETAMODEL_B1950.
Added ELLIPxMODEL_WORLD and POLARxMODEL_WORLD.
Fixed broken PSF-fitting.
Fixed warnings while generating the configure (thanks to S.Pascual).
Pushed version number to 2.9.1.

Fixed random crashes with model fitting (thanks to S.Desai).
Fixed gain problem in PSF fitting.
Pushed version number to 2.8.9.

Re-organized astrometric calls.