Branch for ApgService AIDL development until spec is final
Add first basic implementation of Apgservice

Provides an AIDL-API for other apps to encrypt and decrypt a string
symmetrically with a passphrase. Function names and API is by no way
finalized and will change!

Support for asymetric encription will follow.

For reference and discussion see issue #71,
https://code.google.com/p/android-privacy-guard/issues/detail?id=71
Merge trunk into apg_service
Fix wrong placed backslash
Remove weird chars at the beginning of xml
Allow to regenerate shared preferences

I encountered a problem that changing preferences in APG did not change
the preferences in ApgService after it was called once:

1. call getPreferences
2. change settings in APG
3. call getPreferences again

--> the result at 3. was still having preferences from 1.

To work around this, the function getPreferences has been updated to
force the new generation of preferences while not breaking any other
code relying on the old behaviour.
Reload preferences on call

refs r326
Add connection helper for other projects

This eases using the AIDL-Interface and is the recommended way for other
project to implement the connection.
Remove forgotten line
Redesign AIDL-Interface once more

Using Bundles makes passing data easier and does not need to redefine
the interface if the internel functions change.

The helper class has been updated accordingly. In addition, it wrappes
completely around all input and output (if wanted).
Remove weird line
Remove obsolete import
Reset errors before calling, make some vars final, minor cleanups
Prefix local vars with "_"
Respect options but allow to overwrite them for each call

By default the values set in APG's options are respected now. But they
can be overwritten by special parameters passed through.
Document new args in AIDL
Explain AIDL options a little bit more in detail
Allow helper to clear args and set booleans
Make some things static

*Should* speed up encryption, or better: does not make encryption using
AIDL slower than using APG directly.
Prevent null pointer exception

Error-msg should be better, though.