Automatic Spawning of Target Area

[mhl787156]

This PR adds in the area of interest model and adds it to the default fenswood world.

[mhl787156]

@arthurrichards77 new target shape and visuals:

[mhl787156]

@arthurrichards77 The new update adds automatic spawning of the target area, along with configuration of all elements from number of spawn points to the min distance between hotspot spawns.

• Target spawns at a random angle around the center of the 'annulus'.
• Hotspot spawning achieved via sampling theta and radius values from a Normal distribution around the target.
• Target also fixed to spawn to the right handside of the hill
• Random seed can be set, or target spawn locations can be read in by file.

Here are some sample spawns:

[mhl787156]

Will merge to master when I get the okay from @arthurrichards77 that this is the correct behaviour!

[mhl787156]

Also addresses and closes #9

[mhl787156]

Awesome, it actually wasn't as bad as It could be, definitely a way to go for generation of simple models. Better than xacro nonsense!