add runtime overriding of minReplyDelay with vendor-specific defaults

[kfix]

relates to #42

minReplyDelay should be overridable at the command line (or via env var).

If not overridden, the default should vary based on the vendor of the framebuffer and use a known maybe-good value for the major ones (AMD, Nvidia, Intel).

[kfix]

Lunar did this: https://github.com/alin23/Lunar/commit/81b95cdabb02d37c20c3ebac94fb2e3922e90f40