Dfoxpowell/webinar modal fix

- applied min height and width of 100% to body class in order for fixed position elements to be able to size to 100% without using the CSS vh property
- remove vh javascript from modals.js
- adjust modal styles to 100% height dialog box below 768px and add margin bottom for dialog to account for scrolling of long dialogs about 768px
- change template for create experiment modal
- remove vh checking element from wrapper