Allow dependent variable to be a valid Postgres expression
Added warm-up to FISTA
Added warm-up to IGD

Also updated help messages
Tiny change
Screen out tiny values of IGD result
Make log-likelihood work on GPDB 4.2.3

Also IGD is way too slow on GPDB, added an option to disable parallel
computation.
Added parallel option to IGD, by default it runs on one segment

Parallel IGD is tooooooo slow

Also fixed a bug in IGD

GPDB 4.2.3 works for both now
Finished input, output is almost done
__elastic_net_generate_result generates result extraction function
according to optimizer

outstr_array is a series of numbers if a single array column is given
FISTA output complies with the requirement
Added output support to IGD
Fixed a bug