use /content instead of /download for downloading files

[cagdasgerede]

Note that we could also use /content. Sometimes /download returns binary zip file; for instance:

curl https://android-review.googlesource.com/changes/8299/revisions/1/files/media%2Fjni%2Fandroid_media_AmrInputStream.cpp/download

This is not a problem always since for instance the following returns plain text:

curl https://gerrit.wikimedia.org/r/changes/356858/revisions/1/files/SpamBlacklistHooks.php/download

Not to be broken by the former cases, it would be better to download via /content. However, that returns base64 encoded content; therefore, we need to decode the response before saving it in a file for further processing.

An example on how to decode on the terminal is as follows:

curl https://android-review.googlesource.com/changes/8299/revisions/1/files/media%2Fjni%2Fandroid_media_AmrInputStream.cpp/content| base64 --decode