Preliminary update to the ct8 plugin

Various changes to make the plugin consistent with the current API.
Switch a number of data structures to QT things instead of openCV equivalents.
Make FRsdk::OpenCVImageBody construct either an rgb or grayscale representation
depending on input image type instead of always building both.
Mark failure cases in both the detection and enrollment transforms.
Allow the enrollment transform to work even if eye detection hasn't been done
yet (the sdk will automatically do detection using the default parameters).
Update ct8 cmake files

Target version 8.6.0 of the sdk (this could stand to be generalized somehow)
Link debug versions of the library when building debug configurations.
When building with visual studio, pick the appropriate pre-complied library
for the version of the compiler being used.
Surface the FaceVACS face detector's interoccular distance parameters
Handle facevacs config file location

Export the facevacs directory found by cmake, use that to define a default
config file location of facevacs_dir/etc/frsdk.cfg. Store the config file
path as a property of Globals, allowing users to specify a config file path
as a command line argument to br.exe.
Modifications to openbr_plugin.cpp allow adding dynamic properties (strings
only) to br::Objects.
re-add check in br::Object::setProperty, but only when not adding a dynamic
property.