Question about what files can/should be added to the gmt server

[maxrjones]

Two questions about what files can be added to the gmt server:

1. Are files in gmtserver-admin/cache only for core GMT tests/example scripts or can files be added for PyGMT, GMT.jl, GMT/MEX tests/example scripts as well (e.g., Geologic Unit Dataset pygmt#1364)?
2. What is the preferred file size limit for data added to gmtserver-admin/cache? The current largest file size is ~34 MB, with most files <5 MB. The file referenced in Geologic Unit Dataset pygmt#1364 is ~47 MB. It would be helpful to have file size guidelines for tests/examples.