Completely reworked navmesh_generate_cheap_keepsession
Now goes through the entire map, looking for ungenerated seed poisitions, and then incrementally generates one seed position at a time.

Stupid fix

fixes/tweaks
let stair areas merge in specific circumstances
check for stair areas between merge loops
fix error

only place walkable marks when no navareas are already there

Tweaks!

Fix

Standardized message sending in the backend

Fixed error

Another attempt to fix.

Again