CLI admin diagnostics: only check readability of var folder

In a multi-user environment where group members have permissions to read but
not write the var/ folder of the server, bin/omero admin diagnostics currently
fails with a "Cannot access" exception. This commit relaxes the check_access()
condition of the diagnostics subcommand to check the folder (and subfolders)
readability only.
Merge pull request #3115 from sbesson/diagnostics_readonly

CLI admin diagnostics: only check readability of var folder
Remove reference to keywords. (not used)
Remove keywords
Remove limitation so 3rd party ROIs are visible.
Update UnitsBased for proper enums
Fix parsing of polygon and polyline.
Merge pull request #3184 from jburel/roi-lsm

Roi lsm
Merge pull request #3189 from joshmoore/units-fixes

Various minor fixes for units