Fix for making links have a higher color contrast to other text in blocks. (#2192) ...

The changes were based on the article  https://www.viget.com/articles/color-contrast/

Changes:
 - Link color has been  changed from #337ab7 to #107896.
According to https://webaim.org/resources/linkcontrastchecker/?fcolor=000000&bcolor=FFFFFF&lcolor=107896 (the "Link to Body Text" ratio is 4.14:1 and passes WCAG A test and "Link to Background" ratio is 5.06 and passes the 5.06:1 which satisfies WCAG AA test.)
- The TinyMce editor required new stylesheets to be created.

Fix for issue #1457

Re-introduced the drag feature for the TinyMCE editors. ...

Note that we only allow re-sizing vertically. Resizing horizontally would allow the editor to stretch over
other elements in the flow.

Fix for Issue #2093.

Update asset structure with webpacker gem