JSON float values

Copy of titan.core#609

Summary

JSON decoder can not decode certain float values

Steps and/or TTCN-3 code to reproduce

Encode a float value, such as 1.23456789e-6

What is the current bug behavior?

While JSON-decoding type ...: Failed to extract valid token, invalid JSON format Can not decode type ..., because invalid or incomplete message was received

What is the expected correct behavior?

Decode the float value properly

Titan version

8.2.0

Platform details (OS type and version)

All

/cc @aknappqwt