Fix 'Apply Selected Modifier' operator issues due to improper sequencing, document apply\_modifier a little bit and make it a little less error-prone#1

20kdc wants to merge 2 commits intoSAM-tak:masterSAM-tak/ApplyModifiersWithShapeKeys:masterfrom

20kdc:fixes-520kdc/ApplyModifiersWithShapeKeys:fixes-5Copy head branch name to clipboard