Make this a real library (instead of a submodule)

[ArnyminerZ]

We would have to care less about compile-time settings when this would be a real library. It would be easier to integrate with other projects.

I think of this is a separate library that

• can be added as a normal dependency and then be used in other projects

• has two components, something like a lib and and sample-app directory:

  • lib contains the lib and is what is imported when other projects add the dependency
  • sample-app contains a minimum sample app that also allows to test cert4android in real when debugging (not imported with the dependency)

• make it a jitpack library

• document how to embed the library

• separate demo app from lib ¿Should we?

  • build action for jitpack should only build lib
  • demo app can be opened in Android Studio to test and work on the lib