Add "No grabber" selection to Video source setup

[sphery <mtdean@…>]

The attached patch allows users to configure a video source without a grabber. This can be used with an additional video source for recording from devices such as VCR's or cameras. Without the patch, mythfilldatabase attempts to run the configured grabber to retrieve 14 days of listings every time mfdb is executed. In the case of the DataDirect grabber configured without username/password, this results in fourteen 401's (plus the expected 401's from HTTP auth).

If selected, the xmltvgrabber column for the video source receives the value "none" and the useeit field is set to 0 (in case a user changes from a grabber with which useeit was set to no grabber, but does not explicitly disable and save useeit first). At execution, mythfilldatabase skips the source (with a log message explaining why) without erroring.

I left out usage information (as is shown when eitonly is selected) because trying to explain the issues involved with using a source with no data was too much to cover in the setup page. :)

Also, the patch has the side benefit that because it prevents failures, the post-fillData() tasks (like updating icons and MythFillSuggestedRunTime) actually occur. Until this patch was applied, my MythFillSuggestedRunTime was never updated from the initial 1 Jan 1970 value.

[bjm]

(In [9230]) Closes #1425 by applying patch.

One modification. The field is used to name an executable plus using an English word brings up the question of translation. I've recommended "/bin/true" in the past so using this should work for those who already have this in their existing sources.