Revert "Added source dependency for external/cordova"

This reverts commit b6cc4f7573fba8e1a3c4af62c0279048894c3887.
Added source dependency for external/cordova

Despite having a build.gradle file, Cordova is a source dependency since its unit tests reference missing classes, causing all tests to fail. Removed all explicit dependencies in the example apps, since it is a transitive dependency through SalesforceMobileSDK.

The Maven version of mim4j caused Android lint errors due to missing dependencies on AWT and Swing. The bundled lib seemed to work, so I used that instead.