Fixing for Travis
Changed LintBuildablePrerequisites to check for IPrerequisiteProvider
	instead of ProvidesCustomPrerequisiteInfo, this allows there to
	be other PrerequisiteProviders other than the custom one
Added IPrerequisiteProvider
Changed ProvidesCustomPrerequisiteInfo to allow for multiple prerequisites
	in one info object (+2 squashed commit)

Squashed commit:

[a2aa3a5] Changed LintBuildablePrerequisites to check for IPrerequisiteProvider
	instead of ProvidesCustomPrerequisiteInfo, this allows there to
	be other PrerequisiteProviders other than the custom one
Added IPrerequisiteProvider
Changed ProvidesCustomPrerequisiteInfo to allow for multiple prerequisites
	in one info object

[04be898] TechTreeTrait system has been made
Techlevel UI added
TechLevel UI hidden when no techlevels in mod\nTechlevel dropdown button disabled if only one option