Added IsMutable extension method to type too
Added IsMutable extension method to type too

kshanafelt/commandline,nausley/commandline,Thilas/commandline,huoxudong125/commandline,nausley/commandline,rmboggs/commandline,kshanafelt/commandline,Ehryk/commandline,anthonylangsworth/commandline,Emergensys/commandline,Thilas/commandline,rmboggs/commandline,Emergensys/commandline,huoxudong125/commandline,anthonylangsworth/commandline,Ehryk/commandline