This also validates transaction date and description upon form submission. As noted in
the issue, this removes hledger-web's "smart date" functionality. This
functionality can be restored giving the demand but should be tracked in
another issue.
Previous iterations used input[type=date], but it isn't easily
crossbrowser and the polyfill I found had some quirks.
- the web UI has been streamlined; edit form, raw & entries views dropped
- we now remember whether sidebar is open or closed
- better help dialog
- keyboard shortcuts are now available
- better add form
- more bootstrap styling
- static file cleanups
- report filtering fixes
- upgrade jquery to 2.1.1, bootstrap to 3.1.1, drop select2, add typeahead, cookie, hotkeys
- clarify debug helpers a little
- refactoring