Fix for Sony devices

Crash on picking contacts finally fixed for Sony devices.
Added "Tour"

A Tour will give an introduction to the users telling them what exactly
the app is all about.
Minor bug fixes and UI enhancements

App force close on empty values now resolved. Padding provided to
"Chapter titles" in tour. Selected participants appear already selected
when you press 'Change' (previously was called 'Add') and offers to add
label at the end.
Removed unnecessary boolean