templates: add zapp.yaml template with ui
templates: zapp.yaml bundle section starts empty

This is better than having a "false" file (specified as `- ""`).
This created an error with a stacktrace if the user tries to do `zpm
new`, immediately followed by `zpm bundle`.

Now, if the user tries to bundle an "empty" project, they get a more
meaningful error message.
Explicitly create UI files with zpm new
Fix index.html template rendering

The `zapp` variable wasn't being provided to the template rendering, and
thus was failing.

There was also an issue with `auth_opts` not rendering correctly.
zpm: remove unused function _add_ui
zpm: version robustness in _prepare_auth

For version 1.0 auth, for example, we were expecting the version to be
given as '1.0'. I found a real-world case where it was just '1' instead,
and it pretty much broke the auth option rendering in the UI template.
Merge pull request #187 from larsbutler/zpm-ui-overhaul

ZPM UI overhaul (WIP)