Overload registerMolecule method.
Add method registerFluidChemicalReaction().
Null checks, fix some methods are not static.
Add JavaDoc.
Merge pull request #271 from yushijinhun/api

Add registerFluidChemicalReaction(), overload registerMolecule().
more work on decompRecipeHandling
Merge pull request #272 from way2muchnoise/1.7-update

more work on decompRecipeHandling
extra null check, #270
Merge pull request #273 from way2muchnoise/1.7-update

extra null check, #270