Add more useful error messages on not finding files.

Add useful error messages for errors in finding files related to the GLIMPSE /
EMAF routines.  Also, add check in distance_omnibus.pro to actually stop
running if an error occurs during one of the prob_* calls.

	modified:   create_local_files/omni_glimpse_emaf.pro
	modified:   create_local_files/omni_glimpse_starsub.pro
	modified:   distance_omnibus.pro
	modified:   emaf/omni_emaf_morph.pro
	modified:   subroutines/omni_load_ffore.pro
Minor bug fix in VLINE

Fix minor bug in VLINE w.r.t. the /LOG keyword; trying to take the log of a
negative integer returns zero instead of a floating-point number.  Maybe a bit
of overkill to force DOUBLE precision, but RAM is cheap anymore.

	modified:   utils/vline.pro
Return covariances from utils/linfit_plot.pro

Add ability to return covariances from utils/linfit_plot.pro.  This requires
a pirated version of LADFIT from the IDL library (utils/ladfit2.pro) that
computes the covariance on the initial least-squares fit for return.  Minor
coding neuroses addressed in utils/linfit2.pro.

	new file:   utils/ladfit2.pro
	modified:   utils/linfit2.pro
	modified:   utils/linfit_plot.pro
Add new utility routine for assigning colors to individual points

Add utils/colors_from_values.pro, which converts an input array into an
integer array with bounds [0,255] for plotting using a color table.

	new file:   utils/colors_from_values.pro
Merge branch 'master' into release