Refactor FieldMemberAndAccess Class to use FieldInfo methods were appropriate

This is a refactoring task aiming to replace custom implementations of functions which are already defined within FieldInfo (so to say, have the same functionality/result). For example, in the FieldMemberAndAccess#createGetterMethod(..) the getter-name is constructed by:

String mname = fieldInfo.getMethodSuffix();
...
method = new JMethod(FieldInfo.METHOD_PREFIX_GET + mname, jType,"the value of field '" + mname + "'.");

The bold text should be replaced by fieldInfo.getReadMethod which does exactly the same as above.