[grading-panel]: Re-organized the HAML and JS

Grading panel HAML files in their own area.
First steps towards making the grading panel palatable to the end-customer.
 minor styling changes
Removed last of toolbox/_grd-* files

The files have been rationalized and collated within shared/grading
[grading]: Minor structural and styling changes to the grading toolbar
Merge branch 'master' of https://github.com/abhinavc/web-application