Reasons for creating this PR

There are many warnings originating from Vue and a lot of unnecessary output to console from JS code that could be removed.

Link to relevant issue(s), if any

• Closes Vue framework tuning #1829

Description of the changes in this PR

• Add global config option uiDevMode for loading either production or development version of Vue
• Remove console.logs from JS code
• Mount Vue components only if their mount point exists

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)