remove files from syncing [Feature Request]

[eik-dahms]

Is your feature request related to a problem? Please describe.
It should be possible to exclude files from syncing out of 3 reasons:

1. copyright issues: files or data, that should not appear publicly in the ARC because the user has no rights to do so
2. confidential: data, algorithms that are temporarely confidential
3. big files: user does not want to sync big files

Describe the solution you'd like
to ignore files:
arc ignore <files/folders>
to remove files from ignore list
arc include <files/folders>

[HLWeil]

For this, the .gitignore should be used. Not sure whether it makes sense to also add this functionality into the ArcCommander.

[HLWeil]

Will close this as it's very unlikely I will be working on this.