[OpenMW] Use data entries in openmw.cfg

[poperigby]

OpenMW has its own VFS system, where you can add data=<path> entries to openmw.cfg, and these will be combined at runtime, with later data entries overriding earlier ones. This would be helpful to have over just the normal hardlink deployer, as it will be way faster to deploy.

[limo-app]

Adding this as a deploy mode should not be too difficult. Since this is more of a QoL improvement rather than something necessary to allow OpenMW modding, it may takes some time until i get around to it.