Add @TargetApi annotation for UserManager

We're accessing the android-17 APIs using reflection (which is safe), but
Eclipse refuses to build the project without this.
RulesActivity: Add superuser info to error reports (bug #202)

To aid in diagnosing the various "can't open root shell" issues, report
file sizes for "su" and "Superuser.apk".  Figure out which Superuser
package is being used (if any) and report its versionName.
Merge pull request #233 from cernekee/report-superuser-v1

Add superuser info to error reports; fix Eclipse builds