update library dependencies and remove some sample app cruft

Pruned out some cruft in the widevine sample apps. 

Brought the gradle plugin back up to 0.11.+ to be able to use Android Studio 0.6.1 effectively.

Pulled the library path out into a gradle variable to be set as desired. Currently defaulted to <user home directory>/libs
I think it is bad form to use the home directory for extra files.  Better to create files within the project either in the build directory or outside of it but using ignorable names (for source control).  Perhaps we need a special directory for these downloaded files, say, "downloads/libs" and the like.