Allow parameters in a metric to be replaced at runtime

[lukevenediger]

As a client I want to send in codes that will get swapped out and expanded to more meaningful parameters before being aggregated in the system. For example:

User Agent resolution:

visitor.home.{device-type: ... user agent string ...}.{device-os: ... user agent string ...} becomes
visitor.home.iPhone.iOS7

IP Address geolocation:

customer.login.{city:192.18.17.18}.{city:192.18.17.18} becomes
customer.login.Durban.SouthAfrica

System-specific terminology replacements:

service.load.{module:AAB} becomes
service.load.UserAuthModule

Acceptance Criteria:

• Replacement matchers are plugins loaded at runtime
• A matcher registers itself into the Parser and matches on valid stats lines
• A matcher registers at least one key that will be used to invoke it at runtime
• The format of a replacement tag is {KEY:[Value[, Value]]}
  • e.g.: {KEY}, {KEY:Value}, {KEY:Value,Value}
• If no matchers are found, the metric is sent in as-is

Immediate Uses:

• Swap enum IDs for Names
• Swap IP address for geolocation data
  • Use the free http://dev.maxmind.com/geoip/geoip2/geolite2/ db ?
• Swap user agent string for device data