Overhaul the download and vis functions

[anhtr]

• [x] hpaDownload use an internal table instead of hand coded dataframe
• [x] allow for 'latest_stable' version
• [ ] add a metadata df to the output to show which version the dfs are from
• [x] add option to tidy names (for histology dfs only)
• [x] add option to list what's available downloadList
• [ ] name sure subset, listparam and export work
• [ ] Make sure the vis functions work, especially with untidy df col names