Feat support restructure in mapping model

[schuettec]

Feature: Support restructure operation in mapping model

Before feature: The mapping model for mappings involving restructure operations only contained omit operations for fields that take part in the restructure operations.

After feature: The mapping model now contains all transformations for fields that take part in any nested restructure operation defined by a mapper in the transitive mapping graph. This was done to make any conversion of a source to destination field accesible even if defined by resturcture operation.