v0.3.22

Export metadata, rename toctrees, add link icons

retrieve buildir from app.builder.
export lut data to metadata.json/repotoc.
llow multiple repos to have "subdomains" (to be renamed to "groups").

Rename toctrees as follows:
* subdomain, repos: repotoc
* sidebar, toc: toc
* localtoc, onthispage: localtoc
And suffix with [-_]tree when applicable.

Deprecate  datasheet role.
Add links icons.

Signed-off-by: Jorge Marques <[email protected]>