Use the vue-components for app-navigation and app-content

[raimund-schluessler]

This should fix #804 and lead to a more uniform look of the Tasks app.

Left to do for this PR:

• Find a way to have drag and drop on collections and lists/calendars
• Implement adding a task list
• Properly style the list editing GUI
• Implement the timeout GUI for deleting a calendar

While working on this, I noticed a few other things that should be improved in follow-up PRs:

• Enable to unshare a calendar Allow to unshare a calendar shared with me #819
• Use the colorpicker from the vue-components Use colorpicker from vue-components #820
• Show the user avatars for calendars shared with me and in the share component Show the user avatars for calendars shared with me and in the share component #821
• Switch to newly created calendar after creation Switch to newly created calendar after creation #822

Another thing that should be fixed in the vue-components is the opacity of inactive navigation items and their hover state: nextcloud-libraries/nextcloud-vue#425. Although the proposal nextcloud-libraries/nextcloud-vue#425 (comment) looks very good, there wasn't much progress on implementing it lately. @skjnldsv Should we work-around it here or wait for the issue to be resolved?

[codecov]

Codecov Report

Merging #818 into master will increase coverage by 4.07%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #818      +/-   ##
==========================================
+ Coverage   27.84%   31.92%   +4.07%     
==========================================
  Files          15       23       +8     
  Lines        1142     1253     +111     
  Branches      223      223              
==========================================
+ Hits          318      400      +82     
- Misses        700      729      +29     
  Partials      124      124

[raimund-schluessler]

This should be good now. Drag and drop also works and even sets the background color on hover (which it didn't before). There might be a problem with dropping a task on the app-navigation on touch devices, but I cannot check that since I don't own a touch device large enough for showing the app-navigation and the task list. However, if it really doesn't work there is an alternative way to dropping tasks on the sidebar.

[raimund-schluessler]

Ping @skjnldsv, after #837 it's time to review this PR 😉