Switched on "library project" flag by default for Podio SDK.

This change will break the the tests as library projects won't produce an APK
on their own, they will rather be compiled into the targeting APK when it's
built. There are at least two approaches from here on:

1. Let the test project reference the library project (Podio SDK) and instrument
    itself. While this works (ish), it's a very fragile setup where the code coverage
    tool "emma", for one, will have a rather strange behavior.

2. Create a dummy application project which references the library project. Then
    let the test project instrument on the dummy project instead. While not very
    elegant, it's very stable and predictable.

The following commits will fix the broken test chain by implementing option
two above.
Added dummy project.

This project references the Podio SDK (see the `project.properties` file).
The test project will then be redirected to instrument on this project when
executing the test cases for the Podio SDK.
Redirected the Podio SDK Tests project to instrument the dummy project.

This commit closes the previously broken test chain.
Extended Session tests.
Added default comments to 'ant.properties' in sdk project.