Add FloatCurveKey and OverlapParams types

[bloeo]

[coveralls]

Pull Request Test Coverage Report for Build 2374534430

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 98.876%

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Totals
Change from base Build 1580377184:	0.006%
Covered Lines:	352
Relevant Lines:	356

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💛 - Coveralls

[osyrisrblx]

Closed in favor of #108