remove enum from type parameters allowing to use custom issue types. fix  #359
remove enum from type parameters allowing to use custom issue types. fix  #359

psychopenguin/st2contrib,psychopenguin/st2contrib,pidah/st2contrib,pidah/st2contrib,pearsontechnology/st2contrib,armab/st2contrib,pidah/st2contrib,StackStorm/st2contrib,tonybaloney/st2contrib,pearsontechnology/st2contrib,tonybaloney/st2contrib,pearsontechnology/st2contrib,armab/st2contrib,pearsontechnology/st2contrib,StackStorm/st2contrib,tonybaloney/st2contrib,armab/st2contrib,StackStorm/st2contrib