Add subtasks to the dashboard
Merged master from fguillot
Adding Octicons Font to the assets. Extended make-assets.sh to include the CSS in app.css.
Preview Javascript working again. Moved the code from the board to the task js code. Will need to change the Templates, as the id shall be shorter now (p and w, not preview-tab-nav and write-tab-nav). Will need to work on the elimination of CSRF stuff, too (see Kanboard issue #357)
Changed HTML Code of the textareas to reenable js previews.
Move initialisation of Kanboard.Task.Preview and .Markdown into base.js, so the preview can be used in popover content, too.