Part 3 of 3, continuing PR #7689. This covers 14 idlelib modules and their tests,
rpc to zoomheight except for run (already done) and tooltip (being done separately).

About 10 IDLE features were implemented as supposedly optional
extensions.  Their different behavior could be confusing or worse for
users and not good for maintenance.  Hence the conversion.

The main difference for users is that user configurable key bindings
for builtin features are now handled uniformly.  Now, editing a binding
in a keyset only affects its value in the keyset.  All bindings are
defined together in the system-specific default keysets in config-
extensions.def.  All custom keysets are saved as a whole in config-
extension.cfg.  All take effect as soon as one clicks Apply or Ok.

The affected events are '<<force-open-completions>>', '<<expand-word>>',
'<<force-open-calltip>>', '<<flash-paren>>', '<<format-paragraph>>',
'<<run-module>>', '<<check-module>>', and '<<zoom-height>>'.  Any
(global) customizations made before 3.6.3 will not affect their keyset-
specific customization after 3.6.3. and vice versa.

Inital patch by Charles Wohlganger, revised by Terry Jan Reedy.

M Bindings.py
M EditorWindow.py
M PyShell.py
M config-keys.def
M configHandler.py
M help.txt

1. Annotate the shell window with last restart boundary upon restart.
2. Provide a shell menu entry and hot key (F6) to jump to the last
   restart boundary.
3. Add a new shell menu feature to restart the shell.
4. Update the help menu to add these features.
5. Update the help menu to put text in same order as the menus.
6. Correct a capitalization inconsistency on the Edit menu: Expand Word
7. Rename the "Debug" menu to be "Shell": it's doing more now.
8. Rearrange the "Shell" menu to make the StackViewer entries adjacent.
9. Add a get_geometry method to EditorWindow, which may be of use in
   making window positions persisent.
10. Make <ctrl-v> the "Classic Windows" paste key.
11. Restore decorum on the Help menu by removing "Advice".  As Guido said,
    things will never be the same.  Thanks, David!

Use string.ascii_letters instead of string.letters (SF bug #226706)

"Add Alt-slash to Unix keydefs (I somehow need it on RH 6.2).
Get rid of assignment to unused self.text.wordlist."  --GvR

Much has changed -- too much, in fact, to write down.
The big news is that there's a standard way to write IDLE extensions;
see extend.txt.  Some sample extensions have been provided, and
some existing code has been converted to extensions.  Probably the
biggest new user feature is a new search dialog with more options,
search and replace, and even search in files (grep).

This is exactly as downloaded from my laptop after returning
from the holidays -- it hasn't even been tested on Unix yet.

Features: text editor with syntax coloring and undo;
subclassed into interactive Python shell which adds history.