Minor optimisations and tweaks

[fluffyfreak]

Optimisations parts:

• Inlined methods and added a Normalise-in-place to vector3d
• Batched generating heights, avoid calling GetHeight 1225 times and instead request all heights at once
• Forced override of GetHeight in BaseSphere since it always is anyway
• m_entropy[12] is only used in 2 places and only ever used the first value but refreshed it hundreds of times every Terrain Ctor

Tweak:

• Display the Height and Color fractal names used for a terrain in ObjectViewerView (Ctrl+F10)

These changes probably do affect the terrain generation though I haven't noticed massive changes in testing. Unsure if we'll need a savegame bump