Refactor script block in templates.

C3 is used only in dashboard.html, not elsewhere.
Add Bootstrap.
Make use of Bootstrap

Center the title, add the number of documents in small in it, and an icon of statistics.
Put the paragraph with the link to documents to the right.
Make the content use 10/12 of the page's width.
Make the title a page-header.
Use bootstrap panel

Fix histogram size (configurable).