get Value
Returns ConfigValue.
The order of searching for flags:
Config received from the server with the fetchConfig method.
User defaults from the setDefaults methods.
Method defaults (getDouble, getLong, getString, getBoolean).
Type defaults (0.0 for Double, 0L for Long, "" for String, false for Boolean).
Return
ConfigValue by key if present or null otherwise.
Parameters
key
Config key.