spawns

created spawn concrete entity and list of spawns in gameworld

need test of getspawns
Merge pull request #330 from BU-CS673/production

Production
Merge pull request #323 from BU-CS673/pmd3

Pmd3 -> Production: Bullet collisions & tree growth
Tanks Respawn

tanks respawn after 10 hits

need to write unit tests still
Spawn tests

adding unit tests
Merge pull request #333 from BU-CS673/production

Production -> Brandon
Corrected DrawLayers, fixed most Tank tests

DropPillbox and DropMine tests still failing.
Revert "Corrected DrawLayers, fixed most Tank tests"

This reverts commit 25f5f7fdf53bcb069e51149eecd4797ee2c8df3c.
Damageable Refactor

Refactored the Damageable interface to mirror the methods used in the
Tank class.
Merge pull request #335 from BU-CS673/production

Production
Parser Update

Parser now updates water to grass if a stationary element is placed on
top of the water.
Merge pull request #337 from BU-CS673/Brandon

Brandon
tests

fixing unit tests
merge conflicts with brandon

fixed some merge conflicts due to damageable changes
randomizing respawn

set the respawn location to a random spawn entity
Merge pull request #339 from BU-CS673/pmd-261

Pmd 261