Add auto focus to Delete DB modal

This ticket:
- Updates ModalView to default to focus on the first visible text field
by default.
- Updates the error message when the user fails to type in the database
name correctly.

Closes COUCHDB-2508
Clicking cancel in clone doc modal fix

Before, clicking cancel in the Clone Document modal found on the doc
editor page would redirect you back to previous page. This isn't what
you'd want or expect. Now it just closes the modal.

Closes COUCHDB-2509
Updating classname in CodeEditor View
Refactor CSS for pane layout

 - remove JS hack to have fixed elements on a certain size,
   elements now use position absolute/relative and floating

 - header, breadcrumbs and panes do not overlap anymore, which
   lead to alot of bugs like visible but not clickable buttons
   and problems when trying to add new elements to the header

 - header is now aligned with navigantion/burger-height
   (both 64px)

 - componentize footer for all_dbs page

Parts of this branch are based on a prototype from Sean Barclay
Sean Barclay <fudd1011@hotmail.com> (@seanbarclay)

Closes: COUCHDB-2320 COUCHDB-2271 COUCHDB-2471 COUCHDB-2482