With FlightGear commit 4d36082, the contents of /addon/authors (resp.
/addon/maintainers) in addon-metadata.xml files is now structured. It
may contain an arbitrary number of 'author' (resp. 'maintainer') child
nodes, each of which contains subnodes 'name', 'email' and 'url' ('name'
being mandatory, 'email' and 'url' being optional).
This commit updates Docs/README.add-ons regarding this change in the
syntax for addon-metadata.xml files, as well as the related
modifications to the add-on Nasal interface.
Document new fields:
authors
maintainers
license/{designation,file,url}
url/{home-page,download,support,code-repository}
tags
Add precisions concerning how fields are parsed, a bit more structure,
etc.
Mailing-list discussion:
around https://sourceforge.net/p/flightgear/mailman/message/36155660/
The explicit typing shouldn't change anything for the parsing code in
flightgear/src/Add-ons/AddonManager.cxx, because for each field, this
code knows the correct type and explicitly asks for it (and only once),
but external code might include addon-metadata.xml in some prop tree,
and then the explicit typing is likely to give better results.
Also:
- use the namespace __addon[ADDON_ID]__ when loading an add-on's
main.nas file (previously, the namespace used was __addon[i]__ where
i is 0 for the first registered add-on, 1 for the second one, etc.);
- use logprint() instead of printlog(), because the former writes a
more helpful source file and line number for the log call in
fgfs.log (i.e., not always src/Scripting/NasalSys.cxx...);
- remove the listener once it has been fired;
- add documentation in Docs/README.add-ons.
