Implement persistable changes Object model

[StefanApfel-Bentley]

What
To avoid asking a user for every run how conflicts shall be resolved, we need a way to allow users to define a resolution once and api callers to re-apply these decisions on subsequent merge runs.

The api should not only be limited to conflict resolutions but should also allow to handle any kind of schema changes a user might save away, independent of the actual differences between two schemas.

Goals

• Provide an api to add/create user decisions for a merge
• Changes must be reapplyable and build on top of each other (eg, if a property A gets renamed to A1, merger should know that all changes for A, now need to get applied to A1)
• Simple format to make persistence easier