integration with third party apps: Add import function

[amyburness]

Add import function to Trends.Earth, to offer the option to use not only the JRC Land productivity Dynamics data but also national custom datasets.

[amyburness]

Deliverables for Integration tasks:

• [ ] Customized import tools for other LPD datasets and for the Land Cover Legend Registry (LCLR) of FAO.
• [ ] Adapted GUI for FAO-WOCAT.
• [ ] Documentation of JSON format used to transfer data between Trends.Earth and PRAIS.