Always implement text input "canPaste" property

This is needed for TextField control for instance.
If QT_NO_CLIPBOARD is defined, canPaste will always return false.
Fixes dialogs auto test when QT_NO_CLIPBOARD is defined.

[ChangeLog][QtQuick][Platform Specific Changes] Added canPaste
property to TextInput element also on platforms that don't support
a clipboard (QT_NO_CLIPBOARD is defined).

Change-Id: Ia85205672ba59c1fce70852458c514b03d332de6
(cherry picked from commit c2d802049e48d1d6f0bce6eb0972fb26dc4d6ce3)
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Bernd Weimer <bweimer@blackberry.com>
StocQt demo improvement

Along with general demo improvements, this task implements the new layout
to the StocQt demo. Also few bugs on the functionality are corrected, like
drawing the stock graph on right way and initial values reset on stock
model when changing active stock.

Task-number: QTBUG-38254
Change-Id: I9d3387ed0e3f23512b8e60c70246589c10237818
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>