Refactor qemuCapsParseDeviceStr to work from data tables

Refactor qemuCapsParseDeviceStr to work from data tables

Currently the qemuCapsParseDeviceStr method has a bunch of open
coded string searches/comparisons to detect devices and their
properties. Soon this data will be obtained from QMP queries
instead of -device help output. Maintaining the list of device
and properties in two places is undesirable. Thus the existing
qemuCapsParseDeviceStr() method needs to be refactored to
separate the device types and properties from the actual
search code.

Thus the -device help output is now parsed to construct a
list of device names, and device properties. These are then
checked against a set of datatables to set the capability
flags

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>