* 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.
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.