Reasons for creating this PR

Hierarchies are not rendered in vocabs with multiple concept schemes. This PR fixes rendering these hierarchies

Link to relevant issue(s), if any

• Part of Epic: Hierarchical View Sidebar Tab #1521

Description of the changes in this PR

• Add showConceptSchemesInHierarchy to SKOSMOS object
• Render concept schemes as top concepts in vocabs with showConceptSchemesInHierarchy set to true
  • Use /{vocid}/ method when fetching top concepts on vocab home page
  • Use /{vocid}/topConcepts/ when loading children of a concept scheme after button click in hierarchy tree
  • Use /{vocid}/ when fetching top concepts on concept page
  • Use /{vocid}/topConcepts/ when opening concept scheme page to fetch its children
• Fix getConceptURL method to work when uri space is same as current uri

Addresses requirement 6b in #1521

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)