Add third installation option for the python SDK: our debian/ubuntu packages.

refs #4336
Fix typo.

refs #4336
Wording improvements on the sdk cli installation page.

refs #4336
Make the 'check-environment' blurb stand out more from the regular text.

refs #4336
Link directly to the CLI SDK install instructions.

refs #4336
Add basic documentation for arv keep put and arv keep get.

refs #4336
Refactor the 'Uploading data' page.

refs #4336
Merge branch '4336-improve-upload-data-to-keep-doc'

refs #4336