Action API: add NotNone and numeric values as visibility conditions.

NotNone:  One or more files/folders selected
(Number): That many files must be selected
Make enum values bigger so someone doesn't inadvertantly run into them.
Fix property min
Fix regression from earlier extension case-sensitivity patch.
Fix a memory leak with action activation
Merge pull request #240 from mtwebster/dummy

Actions:  Add more display options: NotNone, and numeric value