Fix Shift-F12 not toggling site inversion

Looks like this was broken by my change to saving scheme names rather
than indices. The issue was further compounded by my mistyping the name
of the scheme in the global default.

Fixes #7
Branch for release 0.3.1
Merge branch 'release-0.3.1'

Changelog:
  * Fix for broken toggling of site delumination with Shift-F12
  * Fixed sites sometimes not using the proper inversion method