Add trenches & dug-in troops

[rogers492]

• [x] en-route to farm
• [x] en-route to ridge
• [x] add MGs

[rogers492]

To add a trench:

1. Make the terrain look like a ditch, add bushes, add sandbags
2. Raise the Visibility on the forward rim of the trench, but don't lower the Visibility behind the rim
3. Troops approaching will not see the trench occupants until they are in it
4. MGs can be positioned on the rim for effective field of fire
5. Troops on the trench (behind the raised Visibility) will not see out of the trench, or be seen from outside it.

[rogers492]

Add a new Location - 48 - to cycle with the patrol at 43 (Group H4), on the critical hill in front of the Ridge.

[rogers492]

Also, add more units, including an officer, to Group H4.

[rogers492]

Closed by #34