Some changes to diffnet.r
----------------------------

 * Improved documentation.
 * est2.my.ev3: no more warning is shown if "length(ss)==0"
   (this warning is difficult to explain to an average user)
 * Changed 'show.trace' argument everywhere to 'show.warn'.
 * Screening methods: set verbose=FALSE as default.
 Some changes:
---------------
 * auxfunc.R: small change in plot.2networks
 * diffnet_ex.R: very minor change
 Some changes:
---------------

 *diffregr.r: change everywhere 'verbose' to show.warn;
              est2.my.ev3.diffregr: no more warning if length(ss)==0;
              other changes related to warning messages.

 *diffnet.r, diffregr_ex.R, ggmgsa.R: very minor changes
Merge branch 'master' of https://github.com/FrankD/NetHet