Updates to graphing adapter

[Evelyn-Johns]

Additions:

• Adapter can tolerate nested structures in config
• Datasets can be added without using config file, in another adapter/project
• Min and max parameters have been added to the tree

Improvements/questions:

• Dictionary/json manipulation functions formatting? (should they be separate class methods?)
• Could replace "location" parameter in config file with a function that generates it automatically?

[ANeaves]

Did you mean to define this method within the load_config method?

[ANeaves]

This feels redundant? why not just keep a single Min and Max value and check each time if the new value is more/less, then update it? If you need it to be the min/max of only whats currently visible, then you can just do what you've done above and do min(data)