Few getter properties added that are used in node_details_base.html file.
Node fields replaced with their corresponding getter properties.
get_common_node_fields() function added that acts as a common method to save node's common fields.
Formatting changes.
Version-history part modified - Implemented Single-verssion and Compare-versions history view.
Merged Heterogenous collections part.
Merge branch 'mongokit' of https://github.com/gnowledge/gstudio into mongokit
group_set field added in GSystem class.
Listing & editing of Pages based on group selection.
conflict resolved after avdoot's commimits
changes in url of images link
conflict resolved
change in file.py
Merge pull request #53 from anujag/mongokit

change in file.py
Added feture
1)created page for video,image
2)edit feture added for video,image
3)now on words download will be downloaded as filename with extension not as id
Merge branch 'mongokit' of https://github.com/gnowledge/gstudio into mongokit

Conflicts:
	gnowsys-ndf/gnowsys_ndf/ndf/views/file.py
conflict resolved