Add BOINC

The app builds fine and is quite usabe, but I have a few questions before this can be merged:

• Is the format of the app description correct? I used the same format as is documented on the wiki, but it appears that most applications use a different format? (The entire metadata was scraped from the app's Google Play entry using a script, so the process can easily be customized without any pain.) Also is inline HTML allowed in the .txt files or not? (The wiki is not clear on that.)
• Would it be possible to handle auto-updates for this app when it has the following caveats:
  • Commits are properly tagged, but their format is: client_release/./.. (client_release/7.8/7.8.6)
  • Releases use the following versioning scheme: .. (<10-letter-hex-commit-hash>) (eg: 7.8.6 (57dd4a4e69))
  • The release number is the Unix timestamp (in whole seconds) of the commit that was tagged for the given release
  • Potentially no part of the Android app source code is touched at all – most releases only update the client binary source code and (maybe) the desktop UI, but not the Android app