Remove redundant activities & a service

IntelliJ revealed some activities and a service in the manifest
which are do not exist.  Additionally, SharedDeckerPicker is no
longer used anywhere.  Both of these are therefore worth removing.

Actually remove SharedDeckerPicker as #hssm suggests
Merge pull request #163 from donald-w/v2.1-dev-RedundantActivities2

Remove redundant activities & a service.