Implement non linear acceleration for missile lib

[godbit]

Implement at method of applying acceleration that is not linear. The (de)acceleration will probably be set as a % value based on the current speed in units %/second. For instance a 32% deaccerlation we result in:

Frame	Speed	Deacceleration per frame
1	524.0	-5.2
2	518.8	-5.2
3	513.6	-5.1
4	508.4	-5.1
5	503.4	-5.0
6	498.3	-5.0
7	493.3	-4.9
8	488.4	-4.9
9	483.5	-4.8
10	478.7	-4.8
11	473.9	-4.7
12	469.2	-4.7
13	464.5	-4.6
14	459.8	-4.6
15	455.2	-4.6
16	450.7	-4.5
17	446.2	-4.5
18	441.7	-4.4
19	437.3	-4.4
20	432.9	-4.3
21	428.6	-4.3
22	424.3	-4.2
23	420.1	-4.2
24	415.9	-4.2
25	411.7	-4.1
26	407.6	-4.1
27	403.5	-4.0
28	399.5	-4.0
29	395.5	-4.0
30	391.5	-3.9
31	387.6	-3.9
32	383.7