[henshin-dev] Model change: support for nested rules

[Christian Krause <henshin.ck@xxxxxxxxx>]

Hi,
I made the following changes to the Henshin model:

1) added the new containment reference Rule->multiRules* : Rule
2) added the new containment reference Rule->multiMappings* : Mappings
3) replaced the eContainer reference Rule->transformationSystem by a 
method Rule->getTransformationSystem()

The class AmalgamationUnit is now marked as deprecated. The editors and 
the interpreter should now be adapted to support nested rules as well. 
Note that the multiMappings reference contains all references between 
the LHS/RHS between a multi-rule and its container rule. The 
multiMappings are managed by the multi-rule, not the container rule 
(analogously to the mappings in NestedCondition).

One remark: the edit and editor code contained a number of manual 
changes which were not in line with the best practices for merging 
generated and hand-written code. As a consequence, I got a number of 
build errors when I regenerated the code. There were a few missing 
@generated NOT tags (I'm not sure whether I got all of them). More 
problematically, some generated classes extend hand-written classes. 
This manual change will be overridden everytime we regenerate the code. 
Therefore, it would be good if you can come up with a different solution.

Ciao,
Christian