wired: implement configuration data flows

wired: implement configuration data flows

- feed stack configuration data provided
by libqtappfw to the ui form;
- forward custom configuration data to
libqtappfw;
- rename staticXXXX properties to customXXXX
- introduce activeXXXX properties to keep the
stack current configuration values.
- fix always invisible placeholder text (qt) bug
by replacing TextField control with TextArea
control.

Bug-AGL: SPEC-2676
Signed-off-by: Raquel Medina <raquel.medina@konsulko.com>
Change-Id: Ib137f8e561ed54179b116acb323485b5b3382ab9
(cherry picked from commit 7bba7c7f9fdffe977fef6714fd9c4ea9caae0a4e)