Move block and weapon prefabs to "Resources" directory

This is for work later to come - Resources.Load requires this structure.
Add in framework for Factions

Faction class represents a faction. Extend it to create a new one.
Factions must implement two methods: get material/weapon. These methods take
integers representing the relative strength starting at 0. Just use a switch
statement to handle that.
Generic represents the original faction from pre-prod Verthex.

SectionMaterials and SectionWeapons can now grab their prefabs programmatically
instead of having them assigned somewhere in the scene.
Change GetPrefab to virtual

SOmetimes this might need to be overridden, for example, Nothing has no prefab,
so it should return null.
Update Builder to use GetPrefab
Update BuildMenu so that it is related to the faction

The BuildMenu looks ugly now, but it is now procedurally generated to show only
the available materials and weapons for a faction.
Update Build so that it properly looks to the Faction

Also introduced a "MoreGeneric" faction for testing purposes.
MoreGeneric just has a different order of stuff to indicate the build menu's
ability to generate itself based on the chosen faction.
Merge branch 'factions' into devbuild