added: high ground (squares with a sight bonus and a range bonus), a map (jl5) which uses high ground, and the possibility for a unit to have (local) range and special range (adjacent squares)

- sight bonus:
  - any ground unit can see adjacent squares if they are lower
  - a ground unit with a sight range of 1 (for example a catapult) will see any adjacent square except higher squares
  - air units will always see adjacent squares (no need to set their sight range to 1 anymore)
- range bonus: a "ballistic" unit (archer, guard tower, cannon tower) can attack a target in an adjacent square if the target is lower