Add methods isInUserProperty() and hasUserProperty() to course expert mode

With isInAttribute("[AttrName]","[substring]") there is a function to test if a substring is part of a AAI-attribute. This should also be possible for regular user attributes. The same also applies for the hasAttribute() method.

Method signature

isInUserProperty("[AttrName]","[substring]")
hasUserProperty("[AttrName]","[string]")
# Example: 
isInUserProperty("email" , "@domain.tld")
hasUserProperty("email" , "@domain.tld")

The methods are available in the expert mode only in the course editor.

ToDo

• Create new method isInUserProperty which is implemented in analogy to isInAttribute()
• Create new method hasUserProperty which is implemented in analogy to hasAttribute()
• Register new methods in ConditionInterpreter.java
• In normal execution, test against user properties
• In course preview, test against user properties from course preview configuration
• Update manual (Method reference / documentation, add example)