* src/plugin-service.c
(plugin_service_file_opener_read, plugin_service_file_saver_read):
Get opener/saver description from translated content of <description>
node inside <information> not from <information>'s attributes.
(plugin_service_function_group_read):
Get category name (both translated and untranslated) from <category>'s
content, not from "name" attribute.

* src/plugin.c
(plugin_info_read):
Get plugin name and description from translated content of <name> and
<description> nodes inside <information>, not from <information>'s
attributes.
(plugin_loader_get_type_by_id, plugin_loader_is_available_by_id,
plugin_db_activate_plugin_list, plugin_db_deactivate_plugin_list,
plugin_db_get_plugin_info_by_plugin_id,
plugin_db_update_saved_active_plugin_id_list):
Removed unnecessary casts.

* src/plugin-loader-module.c (gnumeric_plugin_loader_module_load,
gnumeric_plugin_loader_module_unload): Put (possibly long) g_module
error string in ErrorInfo details instead of appending it to our
error message.