Create fish "cheep cheep" entity

[bouveng]

Create fish entity "cheep cheep".
Unaffected by ground or corals.

4 different types:

• one red, fast - swims in a straight pattern
• one red, fast - swims in a triangle wave form pattern
• one grey, slow - swims in a straight pattern
• one grey, slow - swims in a triangle wave form pattern
• one jumping one for overworld levels

Issue partly resolved with #122