(Define) Multiple rule deletion added, refactored a bit

Refactored two function names so they don't have side effects (plural
object names)
(Define) Bugfix double rule, added equals function to AppliedRule, refactored
(Define) added categories to keycombobox Ruletypes
(Define) Refactored Warnings, fixed button, fixed Dialog, added Close Button
(IconSet) Changed Subsystem icon as requested
(Define) Warning button responding to amount of warnings, earlier bug fixed
(Define) Refactored a lot in Domain
Merge branch 'master' into develop
Fix to saving workspace #16

Modules that were added to a defaultrule didn't exist. Therefore loading
a saved workspace gave errors.
Merge pull request #218 from senkz/develop

Fix: save of workspace!