Simplified exit search algorithm using ray and segment intersection
Portal pillar implemented

1. GatewayTile trait - represents blocks which can teleport entities
1. BlockPortal, represents gateway's transfer zone pillar above gateway block
- Intangible, indestructible, invisible
- Can exist only if supported by any GatewayTile block from below
- If any entity collides it, invokes teleportEntity for the block below it
2. BlockGateway
- no longer reacts on entity walking or activating it
- teleportEntity performs actual search of other gateway and transportation
Issues:
- Portal block render glitch
- Entity teleported to wrong location most of the time
Fixed portal block render glitch, now it's completely invisible
Added some particles to working gateway
Fixed issue with entity's exit position

Cause: no guard for collision direction, so we had 2 exit points instead of one
Issues:
- If player rides minecart through portal, minecart is doubled
- If player jumps through portal, he's teleported back instantly, like he collides with pillar