Guides scripts enabled when multiple drawables selected (fixes issue #7535)
The four scripts accessed via the "Image/Guides" menu entry are all disabled (greyed out) if more than one drawable is selected. These scripts don't care how many drawables are selected.
I have therefore modified them for V3 so that they will be enabled if one or more drawables are selected.
The SF-OPTION for selecting horizontal/vertical doesn't function in V3 so has been replaced with an SF-ENUM of OrientationType. This offers Horizontal, Vertical and Unknown - I have therefore made a virtue out of necessity and selecting Unknown will add both horizontal and vertical guides. The descriptions of the two functions to which this applies have been amended to document this feature in the PDB.
This fixes issue #7535 (closed)