ci: add android builds to CI

[BenjaminAmos]

This is just a small change that updates the Jenkinsfile to use the Android build agent and enables building/publishing the gestalt-android library. I also fixed a compilation error in gestalt=android-testbed that had been previously overlooked when re-naming Component#copy to Component#copyFrom.

This should fix #127.

[keturn]

Is it okay for this android agent to also publish the libraries that Java apps will use, or do we need to build those in a separate environment?

[BenjaminAmos]

The android agent is just a standard java agent with the android SDK pre-installed. I don't think that the android gradle plugin is used unless gradle is directly building an android project. I often leave the android local.properties file in when developing and testing and it hasn't adversely affected things before. I can put the standard java modules and android modules into seperate build steps like Destination Sol does though (see here), which would mean that only the android modules are published from an android-enabled build.