Add support for lower case keys

[rcdmk]

Adds a new property to objects and arrays, allowing the serialization to output only lower case keys:

<%
Dim json
Set json = New jsonObject

json.Load("{""fullName"":""John Doe"",""ID"":123456}")

json.Write() ' outputs: {"fullName":"John Doe","ID":123456}

json.lowerCaseKeys = true

json.Write() ' outputs: {"fullname":"John Doe","id":123456}
%>

A new test was added to test.asp (testLowerCaseKeys flag) to validate the change.

This closes #88.