qt5virtualkeyboard: new package

qt5virtualkeyboard: new package

This patch adds the Qt virtualkeyboard package.

Signed-off-by: Gaël PORTAY <gael.portay@savoirfairelinux.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
[Thomas:
 - use SDPX license codes
 - add entry to DEVELOPERS file
 - drop BR2_PACKAGE_QT5BASE_LICENSE_APPROVED logic, since we removed this option
 - select BR2_PACKAGE_QT5DECLARATIVE and
   BR2_PACKAGE_QT5DECLARATIVE_QUICK instead of using a "depends on"
   and propagate the appropriate dependencies]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>