redo the navmeshes or change the is_player_present code

[plexsoup]

sometimes NPCs think the player is present, because they're on the city block, but the player is unreachable because the navmesh for each little building doesn't extend as far as extents of the city block.

Which means, it could be useful to escalate dynamic navmesh creation. Issue #37

[plexsoup]

I modified buildingTemplate.gd to generate navpolygons for the block automatically, instead of relying on handcrafted bespoke nav polygons.

[plexsoup]

ab50464