UI and Styling Improvements (w/o Drag&Scroll)

[natterstefan]

Tasks / Notes

• css scrollbar styling (vertical): https://gist.github.com/natterstefan/d294080bd0dee372cca03a81fa5c25c9
  - [ ] fix css that causes horizontal scrollbar to stop at 240px (remove/refactor this: https://d.pr/i/8TMgQC/oWBD8tZly6) ==> looks like it is solved ^^
• MuiDrawer-docked-98: has 100% height (full height of the screen) + border (https://d.pr/i/LxVFkA/xzCDNLIj9r)

==> missing CHANGES added in master branch: aa95882

Postponed (will be part of another PR)

• horizontal scroll with Drag&Scroll solution (similar to Trello's DragScroll)
  • https://hew.github.io/react-scroll-horizontal/ (https://www.npmjs.com/package/react-scroll-horizontal)
  • https://stackoverflow.com/questions/40926181/react-scrolling-a-div-by-dragging-the-mouse
  • https://css-tricks.com/pure-css-horizontal-scrolling/ (Example: https://codepen.io/pieter-biesemans/pen/BQBWXX/)
  • https://github.com/qiaolb/react-dragscroll
  • https://smikhalevski.github.io/react-scroll-box/
  • most promising looks this one: https://github.com/asvd/dragscroll (demo: https://asvd.github.io/dragscroll/)
    • Example: https://codepen.io/natterstefan/pen/LrwWJj

[coveralls]

Coverage increased (+0.3%) to 84.236% when pulling b80f1ff on feature/css-styling-adjustments into 52bc7e6 on master.