Refactor Gpumon.load_config

Split load_config into smaller functions for testing purposes.

Signed-off-by: John Else <john.else@citrix.com>
Move config parsing code to config.ml

Signed-off-by: John Else <john.else@citrix.com>
Add type Config.config

Signed-off-by: John Else <john.else@citrix.com>
Add config.mli

Signed-off-by: John Else <john.else@citrix.com>
Add minimal test executable and build rules

Signed-off-by: John Else <john.else@citrix.com>
checkpoint

Signed-off-by: John Else <john.else@citrix.com>