Fix nojoins in List admin.

list.xml uses a nojoins parameter to only list fields from the main
table for e.g. Primary Key selection. However the code to use this was
missing.

This commit adds the code to handle this feature.
Fix plugin filtering on Primary Key selection
Add span classes to bootstrap input widths

Twitter have announced that in future bootstrap input-x classes will
scale font and margins with input box size. This fix adds span classes
to the list to allow user to select these for fixed-font size in future.
Comment out unnecessary statement
Merge pull request #803 from Sophist-UK/misc_fixes

Misc fixes