#7 #15 renaming ball functions

renaming `towardsAway` to `ballTowardsAway`, `towardsHome` to
`ballTowardsHome`, and `moveChip(int)` to `ballMove()`
#7 #15 renaming changeChip to ballPosession

In the Board View, renaming `changeChip` to `ballPosession` and using
static variable identifiers. Also wrote Unit tests for the changes and
updated references in LevelOne