Add ability to construct a new WeatherAPI instance with credentials

[alexanderdean]

Because reading a WeatherAPI.properties on the classpath is too inflexible.

[johnluetke]

Does the changes introduced in 3454682 solve this for you?

[alexanderdean]

It's definitely more flexible but I'd prefer an explicit constructor:

WeatherAPI instance = new WeatherAPI(credentials, lruCacheSize, etc)

[johnluetke]

My only reservation with an explicit constructor is all the overloading that would need to be done for different sets of parameters. Some kind of config object that can be passed in would solve this, however.

[alexanderdean]

As a quick heads-up - Snowplow wintern @AALEKH is working on a PR to add this functionality. We need this to deliver the weather enrichment in Snowplow...