[Custom handler] Protocol listener

[Custom handler] Protocol listener

[Issue#] N/A
[Feature] Handle protocol from custom handlers.
[Problem] N/A
[Cause] N/A
[Solution] Added protocol listener. It will check if widget
was run by appservice and will look for proper page to show.
[ScmRequest] wrt-commons
This patch depends on:
https://tizendev.org/gerrit/#/c/20791/

[Verification] Run manual test from wrt-extra:
1. Run sh registered_handler_register.sh to add widget to appsvc and to custom handlers.
2. Install register_handler.wgt
3. Run scheme_test_tizen.wgt
4. Run mailto link, verify that mailto.html from register_handler.wgt was run.

Change-Id: I3ea18d251999d15df5aaf3fd9d8b3405e3f36bba