* src/command-context-stderr.[ch]: Add.

* src/Makefile.am: Add command-context-stderr.[ch]

* src/main.c (main): Force load plugins before dumping function
definitions.

* src/plugin.[ch] (activate_plugin, plugin_db_activate_plugin_list,
plugin_db_activate_saved_active_plugins, plugins_init): Add
force_load parameter.
(plugins_init): Use virtual function gnumeric_error_error_info to
report error.

* src/plugin-service.[ch]
(plugin_service_function_group_initialize): Add force_load
parameter. Get function info if force loaded.
(plugin_service_activate): Propagate force_load parameter.

* src/gnumeric.h: Declare CommandContextStderr.

* src/func.[ch] (function_def_get_full_info_if_needed): Make
public so that it's available when force-loading plugins.

* src/error-info.c (error_info_print_with_offset): Print to stderr
instead of stdout.

* dialog-plugin-manager.c (cb_pm_button_activate_plugin_clicked):
Add parameter force_load = FALSE to activate_plugin call.
(cb_pm_button_activate_all_clicked): Add parameter force_load =
FALSE to plugin_db_activate_plugin_list call.