Add Basic Flying Saucer Training

[GoogleCodeExporter]

Branch name:
ufotraining

You can find this branch on
https://bitbucket.org/Wuzzy2/hedgewars-wuzzy

Here's a preview of the relevant commit:
https://bitbucket.org/Wuzzy2/hedgewars-wuzzy/commits/058e6286b7179d3d7540f910e92
f6c92d37c8bfa

Purpose of code changes on this branch:
Add a training mission which teaches the basic (and not-so-basic) moves of a 
flying saucer.

Lesson plan:
- Taking off
- Basic flight
- Landing safely
- Managing fuel
- Changing saucers in mid-flight
- Diving
- Dropping weapons from flying saucer
- Firing from flying saucer with [Precise] + [Attack]
- Aiming in flying saucer with [Precise] + [Up]/[Down]
- Underwater attack
- Free flight with inf. fuel and some weapons at end of training

When reviewing my code changes, please focus on:
Whether you like the mission, whether it has no bugs, whatever else you may 
complain about.

Original issue reported on code.google.com by almikes@aol.com on 7 Aug 2015 at 9:08