Add support for HockeyApp "libs" parameter for Android NDK symbols from .so files

[triplef]

HockeyApp for Android supports symbolicating crashes in native (NDK) code by uploading a ZIP of the .so files as described in their knowledgebase:

Put all .so files from the project folders obj/local/$ABI/ into a .zip file. On HockeyApp, click on your version, then on "History" below "Builds", then on the tab "Symbols". There should be a button "Process .so files". Click it to upload the .zip with your .so files, then HockeyApp will dump the symbols and create the symbols.zip.

If you upload your builds through the API, you can set this file as the param libs.

I’d like to propose adding the libs param as an option to the HockeyApp plugin similar to the existing dsym_filename (e.g. libs_filename).

Please let me know if this is something of interest and I’ll go ahead with a pull request, as well as a subsequent pull request exposing this in the Fastlane "hockey" action.