MPS-19118, MPS-19119 - Added and corrected existing checks for Class creators' type parameters' types
Fixed NPEs in EnumConstantDeclaration's behavior and typesystem rules
MPS-19120 - Added checks for improperly positioned non-value types - inside upper and lower bound types and inside TypeVariableDeclaration
Added a forgotten file
Minor polish to BL type variable expansion
Removed a mis-placed comment
Merge remote-tracking branch 'origin/master' into 3.1/vaclavFixes