Remove explicit double quotes from columns.h 'id' entries.

Remove explicit double quotes from columns.h 'id' entries.

The 'id' entries in columns.h are the report field names.  Since these are
unique, we'd like to use them in generation of 'get' / 'set' functions.
As a step towards using them for this purpose, remove the explicit double
quotes and use the macro '#' character to add the double quotes back when
placing them into the '_fields' array 'id' member.