auto-update release version
This MR tries to eliminate the manual editing of .release files.
To update a release, make update-x-release COLLECTION=<collection-to-update> where x is one of patch,minor,major.
This triggers an update to the relative .release of the provided collection with COLLECTION variable. Then, tag field is updated in the root folder .release file. Finally, these changes are committed with an auto-generated commit message (i.e. Update version of COLLECTION to COLLECTION_VERSION) and the commit is tagged.
This enables individual release and visibility of the collection's tag in the git history.
However, right now it only enables one collection to be updated (since it only checks for one valid COLLECTION definition) based on the assumption that in one commit only one collection version must be updated. So in order to publish multiple collections each of them should be triggered, hence the tagging of each commit.
As the last step the commit(s) are pushed to the gitlab. The publish stage is only run if the previous stages are successfull (this may be disabled, will check) and by doing so we ensure that no manual push is necessary to check if the pipeline passes and if it isn't passing then publish is not run.