[EPIC] Sharing NG on Android

Please scope to implement Sharing NG for Android

\cc @DeepDiver1975 @marcelmockkw

EDITED by @jesmrec (draft)

• Preliminary:
  • Check capability oC10/oCIS when opening "Share" in order to inflate existent layout or keep legacy behaviour
  • Check share badges in list of icons (might already work, because ocs support... )
• Share with users/groups
  • List existing shares in oCIS
  • Create a new share over user/group
  • Edit existing share over user/group
  • Delete existing share over user/group
• Share by public link
  • List existing links in oCIS
  • Create a new link over user/group
  • Edit existing link over user/group
  • Delete exiting link over user/group
• Shortcuts
  • Share by me
  • Share with me
  • Share by link
  • Sync & Hide options

Related Issues:

• Preliminary steps https://github.com/owncloud/android/issues/4839
• List existing shares in oCIS https://github.com/owncloud/android/issues/4876
• Create a new share over user/group https://github.com/owncloud/android/issues/4875
• Delete existing share over user/group https://github.com/owncloud/android/issues/4940
• Edit existing share over user/group https://github.com/owncloud/android/issues/4937

No files or tests are named. Start by reviewing the remaining related issues, especially #4940 and #4937, then use the unchecked checklist to scope the work. Done means the remaining user/group sharing, public-link sharing, and shortcut tasks are implemented and verified.