Put downloaded files in public download directory.

It's probably more expected having them in /sdcard/Downloads instead of
/sdcard/Android/data/com.gh4a/files/Download.
Fix typo breaking download in Gingerbread.

DownloadProvider threw a SecurityException, because "true" (the string)
does not equal true (the boolean).
Merge pull request #205 from maniac103/for-upstream

Download fixes