Fix strict warnings in options.js
Debug feature: override detection

Be careful with enabling this feature. I don't know if you get charged
for apps downloaded through this, but better safe than sorry.
Fix detection for paid apps

Previously, the price meta-data was empty (or unset?), but now '0' is
also a valid value. Fixes Lekensteyn/apk-downloaded#9.
Disable auth token verification

This prevents the options page from exposing apparant Alzheimer behavior
where it loses the authorization token all the time.
Valid HTML5 options page, add footer

Also remove annoying indentation and trailing spaces. Use `git diff -w`
to see non-whitespace changes.
Provide feedback when pressing download button
Version 2.0