Change type from string to Text

[pooja1pathak]

FUNCTIONAL TESTS are failing after changing constants.DEFAULT_ATTRIBUTE_TYPE is string instead of Text as mentioned in issue #810 in IoTAgent-JSON in PR #813

Change type from string to Text will be required in test file for successful execution.

[KeshavSoni2511]

Hi, I am working on it

[Nichola-Vaughan]

@pooja1pathak I would like to contribute on this issue. I have submit a WIP pull request.

[fgalan]

After merging PR #1571, I think this issue could be closed.