Reasons for creating this PR

Groups view has not been implemented in the sidebar in Skosmos 3. This PR adds the groups view with basic functionality using Vue.

Link to relevant issue(s), if any

• Closes Implement basic functionality of groups view using Vue #1710
• Part of Implement groups view in sidebar using Vue #1704

Description of the changes in this PR

• Removing sidebar template loading on vocab home page in web controller
• Adding basic functionality of the groups view
  • Loading groups and building hierarchy tree on vocab home, concept and group pages
  • Loading new members for groups on button click
  • Displaying hierarchy tree in UI

Addresses requirement 1 ( + 2, 3.2, 3.3 and 3.5) in #1704

Known problems or uncertainties in this PR

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that show that the new code works, or tests are not relevant for this PR (e.g. only HTML/CSS changes)
• The PR doesn't reduce accessibility of the front-end code (e.g. tab focus, scaling to different resolutions, use of .sr-only class, color contrast)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)