Directives, templates, dir history, SQLite, bugs

- app.js
  - Created several directives: ntlaDir, ntlaCommandEditor, ntlaBrowser,
    ntlaCommand.  Created html templates for each.  Most of them are still
    fairly stub-like, e.g. they don't have their own controllers.
  - Commented out the "before unload" event that says "Are you sure you want
    to close this shell?"
  - Changed the "common" directory dropdown to "recent" directories.
- app_lib.js
  - Added ")" (shift-0) as a hotkey to focus the command window, and clear it.
  - Fixed the "cached" notification in the directory browser.
  - Made the directory browser a bit less "bouncy": instead of assigning a
    "promise" to $scope.dirData (which removes all the directory data until
    data is returned and the promise is fulfilled, which can easily make the
    directory browser close briefly and then reopen a quarter second later), I
    assign to a temporary promise, and then in the "success" callback, assign
    *that* to $scope.dirData.
- browserTemplate.html, commandEditorTemplate.html, commandTemplate.html,
  dirTemplate.html: created.  Moved html from index.html to these.
- index.html
  - moved lots of code to templates
  - Added some buttons positioned absolutely on the right.  They don't
    actually do anything yet.  :)
- server.go
  - Moved to server/main.go
  - Call the new AddHist function to save the directory to the recently-viewed
    table.
- db.go, dir_hist.go
  - Added use of SQLite
  - Store recently-used directories in SQLite.  (Though I don't actually do
    anything with them yet, either.)