New input file format (.fam)

Removed support fo .train files. .train files stored both hairpin and mature
strand sequence for more than one organism. However it also referenced the
foreground files at its top (lines marked with a b).

Introduced the .fam file format, simpler and more identical to a .fax file. It
contains only the hairpin and mature strand sequences required as the foreground
during training. Hairpin sequences to be used as foreground should be
additionally specified when running mirscanTrainer.

A .fam file can also be used as a query file, the mature strand sequences are
ignored.