Ensure that all plugins listed in core section are core plugins
Merge pull request #501 from Icenium/fatme/ensure-core-plugins

Ensure that all plugins listed in core section are core plugins
Fix android emulator when more than one device is used

Remove passing of options.avd to androidEmulatorService as this is a common option and it can be used there directly. AndroidEmulatorService is also part of the lib, so there's no need to pass as argument something that it can easily accessed.
PR comments - add help for retryCount

Add help for retryCount option which can be used in emulate android command.