Minor code editings
More correct code for adding type specification to function declaration with no parameter list
Inlined CodeInsightUtils.createFunctionSignatureStringFromDescriptor()
JetChangeFunctionSignatureAction made nested class of quickfix class (and it does not need to be QuestionAction!)
Minor refactorings in ChangeMemberFunctionSignatureFix
JetVariableDeclaration made JetCallableDeclaration and renamed getTypeRef/setTypeRef, getReturnTypeRef/setReturnTypeRef to getTypeReference/setTypeReference
More renames of TypeRef to TypeReference
JetParameter made JetCallableDeclaration
Simplified quickfix code
Added API in PSI to add/remove modifiers and refactored quickfixes to use it