* configure.in: Make Python plugin depend on python >= 2.0 and
pygtk-2.0. Remove WITH_PYGTK and BROKEN_PY_INITIALIZE
conditionals.

* plugins/python-loader/python-loader.c: Rename all
gnumeric_plugin_loader_python_blah_blah functions to
gplp_blah_blah.
(gplp_load_base): Check for errors from gnm_python_object_get.
(gplp_loader_data_opener_free, gplp_loader_data_saver_free,
gplp_loader_data_fngroup_free, gplp_loader_data_ui_free): New
functions to free loader data.
(gplp_load_service_file_opener, gplp_load_service_file_saver)
(gplp_load_service_function_group): Ref PyObjects in loader data,
and replace g_object_set_data with g_object_set_data_full to make
sure that they are unrefed when loader data is destroyed.
(gplp_func_exec_verb): New function. Invoke a python function when
a verb is executed.
(gplp_load_service_ui): New function. Load UI service.
(gplp_func_file_probe, gplp_func_file_open, gplp_func_file_save):
Remove #ifndef WITH_PYGTK branch. Plugin now depends on Pygtk.

* plugins/python-loader/py-interpreter-selector.c
(gnm_py_interpreter_selector_init): Move meat to
gnm_py_interpreter_selector_new so that errors can be reported.
(gnm_py_interpreter_selector_finalize): Check that py_object != NULL.
(gnm_py_interpreter_selector_new): Check for errors from
gnm_python_object_get and report them.

* plugins/python-loader/py-gnumeric.h (py_new_Gui_object): New
function. Export it.

* plugins/python-loader/py-gnumeric.c (py_CellPos_object_str): New
function. Wraps cellpos_as_string. Returns e.g. B7.
(py_Cell_get_entered_text_method): Fix typo.  (py_Workbook_gui_add):
New function. Add a GUI to workbook.  (py_Workbook_object_getattr):
Add gui_add method.  (struct _py_Gui_object, py_Gui_get_workbook,
py_Gui_get_window, py_Gui_object_getattr, py_Gui_object_dealloc,
py_new_Gui_object, py_Gui_object_type): New struct/functions/variable
to wrap WorkbookControlGUI.  (py_gnumeric_workbook_new): Fix typo.
(py_initgnumeric): Set plugin_info to None when C counterpart is
NULL. Add Gui object type.

* plugins/python-loader/py-console.c (show_python_console): Report
errors from gnm_py_interpreter_selector_new.

* plugins/python-loader/gnm-python.c (gnm_init_pygobject):
Resurrect. This time ask for the gtk2 version of gobject and report
errors.  (gnm_python_object_get): Remove Python 1.5 compatibility
code. Call gnm_init_pygobject.