Problem: it's hard to know the activities included in this repository

[jraddaoui]

Is your feature request related to a problem? Please describe.

Looking at this repository it's hard to know what activities are included in it and how to use them.

Describe the solution you'd like

I'd like to propose a re-organization of the activities in this repository, following the pattern used in the activities from this WIP PR (https://github.com/artefactual-sdps/temporal-activities/pull/25). In general, I'd like to:

• Have a single package for each activity.
• Use the same naming convection inside all activities (Params, Activity, New(), etc.).
• Add a readme file inside each package/activity explaining it's dependencies, behavior and usage.
• Improve the main readme, adding a small comment of each activity and linking to their own readme.

This is how I initially envisioned this repository and something that @fiver-watson already mentioned a while ago. It will require changes in the projects using the existing activities but I think it's not too late and better do it now.

[jraddaoui]

Proposed package names for the existing activities:

• archiveextract
• archivezip (added in #27)
• bucketdelete (added in #25)
• bucketdownload (added in #25)
• bucketupload (added in #25)
• bagcreate
• bagvalidate
• removefiles
• removepaths
• xmlvalidate