Resolution of some high-priority issues

This merge request includes fixes for the following issues:

• #842: [Timeline / Timeseries] - Zoom selection is different to actual enlarged area
• #843: [Settings - General] Redundancy with Snowheight Autoscale
• #850: Time series: use left and right arrows to navigate
• #856: Title of niviz simple profile not usable for mobile devices
• #881: Timeseries: adjust y-axis range manually
• #885: Time zone lost when exporting to JSON

Still in progress:

• #686: PRO parser support for SK38

Also working on an analysis for the rest of the milestone: "Fix niViz issues in current code".

This merge request also includes some maintenance changes:

• Upgraded node-sass from v4.9.0 to v4.12.0 due to missing binary distribution of node-sass v4.9.0
• Fixed (downgraded) bootstrap-sass-official to version 3.3.7 in order to fix dependency compatibility issues causing syntax errors (similar to https://github.com/twbs/bootstrap/issues/33046)
• Fix duplicate key error in .eslintrc
• Add package-lock.json to version control as recommended by npm to get the exact same dependency tree (https://docs.npmjs.com/cli/v6/configuring-npm/package-locks#using-locked-packages)
• Add exception handling if git tag not available during build
• Updated readme instructions for build