FR: webapp - visually represent "skip this acquisition"

[pvavra]

By setting the tag to "hirni-dicom-converter-ignore", one can skip a specific dicom-series during the spec2bids step.

To more clearly visually communicate this fact to the user, I suggest to extend the webapp GUI by:

1. adding a checkbox for "skip this dicom-series"
2. greying out (and thus making impossible to edit) all the fields of the series.

re 1:
by checking/unchecking the box, the correct tag would get added/removed automatically

re 2:
to visually represent that a series will be skipped, the values should be "frozen" - like by the "valid" checkbox on the right. However, the values should be kept, in case the user decides later to not-skip the series after all..