Cleaned stuff up a bit

Removed useless things
Created an Immovable Crate Object

Now busy tweaking things so that the crate actually doesn't move.
problem comes in with collision resolution.
Fixed Collisions, Implemented Immovable Crate

Collisions, even those created by rotation, is now managed. objects
slowly get moved apart when they overlap, if they have some velocity
their movement to get where they are is recursively undone.

Immovable Crates now don't move ever.

Tail-whip bug
Some problem with react(...) of tanks causing them to behave weirdly
when one tank is being propelled and turns into another tanks which
isn't being propelled. Short term solution: reduced the effect of
react(...) for tanks, it is still in place though, allowing tanks to be
pushed around by other tanks.
Updated GameLogic

GameLogic now has, and checks a vector of shared_ptr to
SGSImmovableCrate

Started seperating sfml stuff grom GameLogic and placing in
SfmlInterface.
Changed timing, started boundaries.

Having hundreds of crates as a boundary slows the game down
unnecessarily.
Boundary Update

Eastern boundary, when set at x>=100 sucks the player in, rather than
pushing him out. I have no idea why.
Fixed boundary collision problem

Gave up on the whole notion of a collision point. Normals, in collision
resolution, seem to now reliably point out of an object. (Huzzah!)

Also wrote a test for: Coordinate GameObject::avgInside(GameObject)

Fixed the rocket sprite at some point today.
Misc

Changed all GameLogic vectors to lists.
Made rockets disappear when they hit a tank.
Removed dependency on sfml timer

Final commit before ripping GameLogic Apart to seperate it from SFML.
Removed Unnecessary Layer of Separation

Game Objects could only interact with SfmlInterface through being a part
of an SfmlGameObject. This was removed. Textures are now loaded in the
Sfml Interface itself and shared between sprites.