Add German translations and fix English texts.
More workspace settings.
First step towards avoiding to re-download an old issue.

Fors this we create a new directory to put the issues in.
When we are about to download a new one, we first check if
it already exists. If it does, we simply open up the existing
file. If it doesn't exist, we delete all old issues to preserve
space, and the proceed as usual to download and show the
current issue.

Still left to do: Parsing the file name of the issue from the
current ePaper web service. Right now we use the timestamp, which
of course always causes the issue to be re-downloaded.
Fix 'impossible to download after resume' bug.
Switch to using a glue library so that source is accessible.

Before we had the class older of the library in the classpath
of the Android project. This submit changes this to having
a library project which depends on the pure Java project.
This way, navigating to code in the Java project works as
expected.
Ensure filename is based on download URL.

With this, the file name of each issue is unique. Together
with the previous change to only download an inssue again if
it isn't present on the device right now, this change will
not download an issue again if it is already present.