solve the register and masking entanglement

i summed up some questions:

for every function call lets assume:

• the function has a source and a target
• source and target can be a single column or a collection of columns
• source and target could be the the same

the following questions need to be answerd:

1. will any flags be altered ?
2. will any data be altered ?
3. will the index be altered (this always alter flags and data) ?
4. will new data-columns be generated ?
5. will new flags-columns be generated ?
6. does data source(s) needs masking ?
7. does data source(s) needs demasking ?
8. does data target(s) needs masking ?
9. does data target(s) needs demasking ?
10. does target(s) flags needs squeezing ?
11. does sources(s) flags needs squeezing ? - only if target==source

extra questions:

11. what happens if target is the same as source
12. what happens if some targets are in sources
13. what happens if some sources are in targets

@luenensc, @schaefed