add baremetal plugin

This patch adds the baremetal plugin. The baremetal plugin is for
debugging small targets with hardware debugger where the remote linux
plugin does not fit. It adds a new kit and device class of type
baremetal. The device allows entering custom gdb commands. Currently only
qmake builds are possible. To use this with smaller devices without qt
a fake-qt installation is needed. CMake and qbs is currently not
supported.

Change-Id: I86816f897a2e9ed8b95e3184387969cedf8a14d7
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>