add read Json method to IOTools

[mgaldzic]

for Deserializing a Collection with Objects of Arbitrary Types
gson requires using Gson's parser API (low-level streaming parser or the DOM parser JsonParser) to parse the array elements and then use Gson.fromJson() on each of the array elements.

http://sites.google.com/site/gson/gson-user-guide#TOC-Collections-Limitations

I'll need to study this carefully as Custom Serialization and Deserialization may be needed to deserialize from json