Adding Appium support for Saucelabs

Capabilities that we need to run Appium on Saucelabs https://support.saucelabs.com/entries/51370580-Android-Desired-Capabilities

This is for issue https://github.com/mozilla/pytest-mozwebqa/issues/122

Jenkins Build : http://selenium.qa.mtv2.mozilla.com:8080/job/marketplace.dev.mobile.saucelabs.appium/