Fix JSON encoding of double parameter values

[ahoenerBE]

Public API Changes Adds an optional parameter numberTypeHint to hint when parameter values should be encoded as doubles

Description JSON stringification will cause a whole double value (e.g. 1.0) to be encoded as an int value ("1"). This will cause a rejection from the ros2 parameter service call unless dynamic typing is enabled, because it incorrectly interprets it as an int when the parameter type is Double.
This PR adds a JSON replacer to the parameter encode to make sure that even if it's whole it has a decimal point.