add bypass header config option to maxmind_acl plugin

[traeak]

This adds support to use an optional header and value to bypass running this plugin in the TSRemapDoRemap stage.

maxmind config yaml looks like:

maxmind:
 bypass:
  header: "@BypassMe"
  value: someval

If this option is not provided then the plugin runs as normal in enforcing mode.
'value' is optional. If missing only the presence of the header is checked.a