view doesn't limit to bootstrap containers

[Wim-van-der-Veen]

I noticed that both the 'grid' and the 'gantt-activity' containers use a fixed width, whereby the 'gantt-activity' width depends on the screen size. That does conflict with my bootstrap-4 (beta) setup. I am planning to change this (locally). If you're interested, i can submit that code (once finished).