Possibility to add dependency to another commit in Coin

Problem:

Currently if two commits on different components are dependent, it takes a long time before the later can be included. Say B uses API provided by A. If I want to change the API, the sequence is following:

1. Add new function to A, which is used by nobody
2. Wait until A gets merged
3. Wait until qt5 submodules update has been done
4. Change B to use the new API
5. Wait until B gets merged
6. Wait until qt5 submodules update has been done
7. Remove old function from A

If several components depend on the API to be changed, this gets even more complicated

Proposition:

Add "Depends-On [Change-Id]" notion to Coin. Coin would then know these components need to be built together. Sequence would then be:

1. Change API in component A
   • Change-ID = AAAA...
2. Change component B
   • Depends-On: AAAA...
3. Change component C
   • Depends-On: AAAA...
4. Let Coin automatically take care of the integration order