More skip options

[michielbdejong]

IIUC the current default behaviour is:

• load from snapshots (for 'pre run')
• record version ('pre run')
• fetch source documents
• record snapshots
• load ('read back') from snapshots
• record version

And the extractOnly flag changes this to:

• load from snapshots
• record version

I would like to have the following behaviour in our instance:

• skip the pre run (IIUC this is only needed if the declaration or the software version changed, and we can do an explicit pre run in those situations)
• skip the read back
• maybe even skip the recoding of snapshots altogether.

So the behaviours I would like to have access to would be:

1. skipPreRun + skipReadBack:

• fetch source documents
• record snapshots
• record version

2. skipPreRun + skipSnapshots

• fetch source documents
• record version

I'll create a PR that adds the skipPreRun, skipReadBack and skipSnapshots options, OK?