Add option to import raw json config directly when creating new dashboards.

[christabor]

When building a new dashboard, it would be nice to be able to drop in an entire config with the raw config directly, instead of creating modules one at a time.

For example, this one is a fairly involved: https://github.com/christabor/flask_jsondash/blob/master/examples/config/kitchensink.json

Certain elements would need to be stripped out, and would not get written directly as-is to the database, for security and safety (or relevance: e.g. postgresql will not store the data exactly the same).

Another useful reason for this is that since the project is meant to encourage "decentralized dashboards" by housing data elsewhere, in an open-ended fashion, this means sharing configurations would be easy and promote a community of dashboarding (in the same sense as ipython notebooks), while being open source and self-hosted.

Requirements:

• Strip out guid on all modules and regenerate
• Strip out ID entirely
• Strip out date, and regenerate based on import time.

These should all happen server-side.