Squashed 'moose-gui/' changes from 38da92b04..5d7f7633f

5d7f7633f Too many python3 incompatibility issues. For now on, gui is only compatible with python2.
599dbd6d3 Testing with python3 as well. If python3 support is not intented, we can fallback this commit.
83be02e60 changes made after addition of groups, some of action are implemented
24cba7d6f  some more clean
cdf16259d at file load dialog, a clean round trip is done
08fc6cd0b at loading time, kkit model is checked for the atleast for 1 compartment and atleast 2 species
373efaa6d check if moose object already exist, if yes use element, else create a object
e37368553 in mousePressEvent further check made for group object along with compartment and other moose object
ae6265ed8 travis is failing, while installing python-libsbml trying to fix providing -H
c70f30098 some clean up with co-ordinates while saving into XML files
dd177002c wrong comparsion with path and moose object was done corrected
24ecdccac some clean up with groups
84be91147 changes made ...