Class parameters and parameter conflict detection
Improved formatting of class parameter conflicts popup.
Node and Group 'Parameters' were renamed to 'Variables'.
A spec was changed to be in compliance with new naming - group and node 'Parameters' were renamed to 'Variables'
Performance optimizations - foreign key indexes were created, OpenStructs were replaced with Hashes.
Improved conflict reporting
UI changes for variable and class parameter conflicts.
Class parameter changes were improved to be in compliance with Rails 3.
RSpec tests were fixed.
Minor simplifications in conditions
(maint) DRY up membership update and delete

Prior to this commit, the membership controllers had virtually the same
code for `update` and `delete`. This commit abstracts away the
differences to have a single source of truth for the respective logic.