Update cmake-dependencies: clarify HunterGate
Update cmake-dependencies: clarify HunterGate

- don't mention git submodule
- don't merge hunter dependencies and add_subdirectory
caseymcc/hunter,xsacha/hunter,akalsi87/hunter,isaachier/hunter,zhuhaow/hunter,fwinnen/hunter,Knitschi/hunter,pretyman/hunter,dmpriso/hunter,dmpriso/hunter,tatraian/hunter,Knitschi/hunter,shekharhimanshu/hunter,ruslo/hunter,madmongo1/hunter,NeroBurner/hunter,mchiasson/hunter,ErniBrown/hunter,ingenue/hunter,caseymcc/hunter,x10mind/hunter,dan-42/hunter,ledocc/hunter,madmongo1/hunter,shekharhimanshu/hunter,RomanYudintsev/hunter,dvirtz/hunter,zhuhaow/hunter,tatraian/hunter,ErniBrown/hunter,designerror/hunter,pretyman/hunter,xsacha/hunter,ikliashchou/hunter,pretyman/hunter,akalsi87/hunter,RomanYudintsev/hunter,ikliashchou/hunter,xsacha/hunter,xsacha/hunter,fwinnen/hunter,isaachier/hunter,zhuhaow/hunter,vdsrd/hunter,mchiasson/hunter,vdsrd/hunter,x10mind/hunter,dmpriso/hunter,ledocc/hunter,ruslo/hunter,vdsrd/hunter,NeroBurner/hunter,designerror/hunter,isaachier/hunter,NeroBurner/hunter,Knitschi/hunter,isaachier/hunter,pretyman/hunter,ledocc/hunter,akalsi87/hunter,stohrendorf/hunter,NeroBurner/hunter,madmongo1/hunter,ingenue/hunter,dan-42/hunter,fwinnen/hunter,ErniBrown/hunter,stohrendorf/hunter,ruslo/hunter,dan-42/hunter,mchiasson/hunter,ingenue/hunter,ikliashchou/hunter,dan-42/hunter,stohrendorf/hunter,dvirtz/hunter,ingenue/hunter,x10mind/hunter,ruslo/hunter,shekharhimanshu/hunter,designerror/hunter,mchiasson/hunter,dvirtz/hunter,tatraian/hunter,RomanYudintsev/hunter,ErniBrown/hunter,madmongo1/hunter,caseymcc/hunter,ikliashchou/hunter