Changed CONCENTRATION_MODEL to SPREAD_MODEL.
Added SPREADERR_MODEL measurement (currently a crude estimate).
Optimized FFT calls.
Set PSF_NMAX to 2 by default.

Removed singular matrix warning.
Added MATRIX_MODELERR measurement parameters.
Added DURATION_ANALYSIS measurement parameter.

Added computation of FLUXERR_MODEL and MAGERR_MODEL.
Fixed a numerical bug in E1MODEL_IMAGE and E2MODEL_IMAGE.
Improved onscreen display.
Pushed version number to 2.8.7