Removed DHTMLXTREE code residue

Grepped the code for all DHTMLXTREE related occurrences. 
For e.g. -
1. node['id']
2. node['text']
3. node['im0'], node['im1'], node['im2']
4. node['item']
and deleted/addressed it.

#118
@h-kataria The commented line above has been in the commented state since February 10, 2010 (checked that with the Annotate feature in RubyMine). I got rid of it because it made a DHTMLXTREE reference - ```a_node['text']```.
The ```.inspect``` was removed earlier in the year when we converted the trees to dynatree. I'm assuming it must have been tested back then.