* Tkinter functions and constructors which need a default root window
raise now RuntimeError with descriptive message instead of obscure
AttributeError or NameError if it is not created yet or cannot
be created automatically.
* Add tests for all functions which use default root window.
* Fix import in the pynche script.
failure when the test is ran the second time.
The root attribute was set in parent class in setUpClass and then
overridded in child class in tearDownClass.
window is created for every test class.
Fixed Tkinter images copying operations in NoDefaultRoot mode.
Tcl command names generated for "after" callbacks now contains a name of
original function.
Serhiy Storchaka