Remove tpk and wgt backend code

Remove tpk and wgt backend code

Source code is being transfered to separate git repositories.
This repository will export devel package for those backends.

Requires to be submitted together with commits moving source
code of backends to repositories:
 - platform/appfw/wgt-backend,
 - platform/appfw/tpk-backend.

Submit with:
 - https://review.tizen.org/gerrit/#/c/54291/,
 - https://review.tizen.org/gerrit/#/c/54886/.

Change-Id: I7a4ba6f6dd732418ae896130010d22c99ceb8e30