Return Collection<CryptSLRule> where possible

[AnakinRaW]

Motivation:
Currently most code (unnecessarily) returns a List<CryptSLRule>. Using the more generic type Collection would allow us to use List but also unsorted collections like HashSet simultaneously.

Tasks:

• Discuss whether a forced sorted collection (List) is essential or could be substituted with a Collection
• Discuss about other code where this might also occur.

If approved:

• Perform code change everywhere appropriated.
• As this is a major API change and will cause incompatibility change the minor version digit of the version number.
• Apply changes to the IDE plugins