[QA] Fix compiler warning from previous commit
SF Bugs#113: Fix waypoints can be accidentally moved on (re)selection by the select tool

Add specific flag for detecting delibrate movement within the TrackWaypoint handling.
Also fix incorrect function definition for select move.
Hence replace the removed button state with a 'something selected' flag.
Remove unnecessary restriction on GeoRef layer needing to be in UTM Mode.

Although currently setting the Ref points needs UTM input the drawing doesn't need to restricted that way.
GeoRefLayer is always created before the properties dialog is called.

Thus simplify the pointer usage and remove the unused create/setup.
Extend file entry to enable running a callback on entry accepted.
Refactor world file reading to be more reuseable and improved comments.
By default automatically attempt to read the associated world file of a new georef image.

A preference allows turning off this attempt.
GeoRef Layer improvement to offer entering coordinates in Lat/Lon.

Optionally work out MPP values if the lower right coordinate is entered.

For Lat/Lon <-> UTM conversion actually store UTM zone and letter rather than the implicit value of the viewport.
Move function to apply an alpha value to be reuse-able.
Add alpha capability to GeoRef images.
[DOC] Shift GeoRef layer help into a separate file.
[DOC] Update GeoRef Layer documentation for the latest capabilities.
Merge branch 'GeoRefImprove'