Based on OrbotHelper from libnetcipher, with logic from i2p.i2p-bote.android

i2p.i2p tag: i2p-0.9.15

Changing this requires changing the import path of the generated R file, which
will unnecessarily affect most of the code. R is built in a package based on
the AndroidManifest.xml package name, whereas the final app package name is
overridden in app/build.gradle for free and donate versions.

Untested, we need to find x86 and MIPS devices to test with.