[IZPACK-1061] - UserInputPanel: Installer crashes on missing 'set' attribute for RuleInputFields
Merge branch 'IZPACK-1061' of https://github.com/rkrell/izpack into rkrell-IZPACK-1061

Conflicts:
	izpack-panel/src/main/java/com/izforge/izpack/panels/userinput/field/rule/RuleField.java