Iteration 1 for file detail & new sharing

[AndyScherzinger]

WiP for #2485 and collab with @tobiasKaminsky

• refactored the details screen to have 2 tabs for activities and sharing including swipe left/right for activities/sharing
• add activities loading on a per file basis (possibly needs a server API change)
• clarify "star use"
• implement star / keep available offline (after discussion)
• move overflow menu from top to Filename "row"
• remove sharing icon from top menu
• make header transparent, only back arrow visible (for preview-able files), non-preview-able files do not have any icon/preview, so that the first "row" is file name (and then we can show again a solid header).
• add previews
• add preview-able/non-preview-able toolbar handling
• fix pull-to-refresh on activities tab
• fix theming

Remarks:

• add commenting and sharing option via separate PRs after this one is merged

What do you think @tobiasKaminsky @jancborchardt ?

Actual WiP UI-wise

[AndyScherzinger]

Added initial loading of activities (copied the code from the activities activity, so not file specific yet):

[AndyScherzinger]

@nickvergessen any hints on how to just load the activities of a given file? https://github.com/nextcloud/activity/blob/master/docs/endpoint-v2.md did give me any hints and the web UI is capable of doing so while I of course don't know if the web UI uses an API which allows for that and is also exposed for other clients.

[mario]

👍

[AndyScherzinger]

I'll soon start with Iteration 2 for follow up on this PR.

Things to be done

• adding further functionality described in Roadmap: file detail & new sharing #2485
• technical cleanup
  • listview->recyclerview
  • butterknife
  • MVP-ing
  • avatar fetching

Happy for any collaboration @tobiasKaminsky @mario @ardevd