Add more filter options

[aawsome]

I think having more filter options would be very nice.

Some ideas (names need to be discussed)

• filter-before or filter-older-than to filter out too old snapshots
• filter after or filter-newer-than to filter out too young snapshots
• filter-size-greater-than
• filter-size-lower-than
• filter-tags-exactly to allow to specify one or more exact taglists to filter in contrast to filter-tags which does filter by any tag which is given in one of the provided taglists

[simonsan]

Fixed by #1263