allow for elton to use zip archive as cache dir.

[jhpoelen]

Currently, you tell elton to use a specific cache dir by saying:

elton ls --cache-dir=some/folder/

however, some publications use an archive zip of the cached datasets, so suggest to also support:

elton ls --cache-dir=some/archive.zip 

This way, you can more easily work with immutable collections of datasets.

[jhpoelen]

With Elton v0.14.2, you can stream process DwC content from the GIB provenance logs.

from https://github.com/globalbioticinteractions/elton/releases/tag/0.14.2

GIB_VERSION=hash://sha256/37bdd8ddb12df4ee02978ca59b695afd651f94398c0fe2e1f8b182849a876bb2
CONTENT_REPO=https://linker.bio

preston cat --remote $CONTENT_REPO $GIB_VERSION --no-cache\
 | elton stream --data-dir data --remote $CONTENT_REPO --no-cache

see #52

This allows for a way to work with immutable datasets containing DwC-A or other content.