Initial libWacom support

Summary:
Store vendor ID in tablet information when detecting connected tablets.
This is later used for libWacom lookup.
Look up tablet information via libWacom if tablet is not found in local
and system device databases.

Test Plan: temporary removed tablet definiton from the bundled DB and checked that it still works with libwacom picked defintion

Reviewers: fvogt, xuetianweng

Reviewed By: fvogt

Differential Revision: https://phabricator.kde.org/D11973