add more default configuration to sphinx conf.py

Add values extracted from package.xml to the wrapping sphinx config.py. This eliminates the need for packages with custom config.py to duplicate author, copyright and version information from package.xml.

rosdoc2/verbs/build/builders/sphinx_builder.py

@@ -72,6 +72,10 @@ def ensure_global(name, default):
 
 ensure_global('rosdoc2_settings', {{}})
 ensure_global('extensions', [])
+ensure_global('project', "{package_name}")
+ensure_global('author', "{package_authors}")
+ensure_global('release', "{package.version}")
+ensure_global('version', "{package_version_short}")
 
 if rosdoc2_settings.get('enable_autodoc', True):
     print('[rosdoc2] enabling autodoc', file=sys.stderr)
@@ -643,7 +647,12 @@ def generate_wrapping_rosdoc2_sphinx_project_into_directory(
             'user_conf_py_filename': esc_backslash(
                 os.path.abspath(os.path.join(user_sourcedir, 'conf.py'))),
             'breathe_projects': ',\n'.join(breathe_projects) + '\n    ',
-            'intersphinx_mapping_extensions': ',\n        '.join(intersphinx_mapping_extensions)
+            'intersphinx_mapping_extensions': ',\n        '.join(intersphinx_mapping_extensions),
+            'package': package,
+            'package_authors': ', '.join(set(
+                [a.name for a in package.authors] + [m.name for m in package.maintainers]
+            )),
+            'package_version_short': '.'.join(package.version.split('.')[0:2]),
         }
 
         print(os.path.abspath(os.path.join(directory, 'conf.py')))