Add routes for repository tag editing.

This is to fix the following error:

Error caught: [ActionController::RoutingError] No route matches
{:action=>"tagging_edit",
 :id=>nil,
 :db=>Repository(...),
 :escape=>false,
 :controller=>"repository"}

http://bugzilla.redhat.com/show_bug.cgi?id=1138120
Add missing route and a spec fix

http://bugzilla.redhat.com/show_bug.cgi?id=1138120
Don't sort non-sortable columns

Non-sortable columns, such as row_button, would have grid_obj
set to an empty string.

https://bugzilla.redhat.com/show_bug.cgi?id=1132536
Merge pull request #510 from mzazrivec/fix_repo_tag_routes

Add routes for repository tag editing.
Merge pull request #531 from mzazrivec/button_columns_nosort

Don't sort non-sortable columns
Missing Virtualization Type column for Amazon Images

https://bugzilla.redhat.com/show_bug.cgi?id=1139835

The UI was not displaying the Virtualization Type for
Amazon Images.
Merge pull request #548 from mkanoor/missing_textual_summary

Missing Virtualization Type column for Amazon Images