Add three different ways to access TERRA-REF trait data to the OSF page

[MagicMilly]

Reason Create a TERRA-REF OSF page for an introduction of working with the data (starting with trait data), with programmers/analysts/researchers/learners of various skill levels in mind.

Tasks

• [ ] Start with a section to help users decide which method is most appropriate for them
• [x] Add Dryad data with easy download for beginners
• [x] Instructions in wiki for beginner download
• [x] Add R code for querying data for R programmers
• [x] Include and link to Kristina's tutorial for R code
• [x] For more advanced learners, include and link to instructions for connecting to betydb using Docker and PyCharm
• [ ] In wiki, include prerequisites for each method
• [ ] In wiki, also include resources to learn and read more about the different prerequisites (e.g. SQL statements)

Desired Result Have three methods for accessing data and documentation for each on the Using TERRA-REF Data OSF page

[MagicMilly]

Do not have a public link to the OSF page yet, but I added three wiki pages with the minimum viable information to access TERRA-REF data via download (beginner), R and RStudio, and Docker and SQL (advanced). Next ticket will include more information about prerequisites and links to resources appropriate for each level.

Follow-up issue #289