Get Jena working on Android

Currently, Jena can't be used on Android as is, due to multiple issues caused by differences between the standard JVM and Android's Dalvik VM.

The main issues are

1. Package conflicts
   1. The StAX API (javax.xml.stream is missing on Android). It's not possible to just provide the classes as including packages from core Java namespaces doesn't work.
   2. Android provides an ancient version of httpclient that is incompatible with version 4.2 required by Jena.
2. TDB uses java.lang.ManagementFactory in ProcessUtils which isn't available on Android. It's possible to use android.os.Process instead but that requires a dependency on the Android SDK.

There is a project that does some post-processing on the Jena packages to create a variant that runs on Android. Some of it might be of use to get Android support into mainline.