bpo-33051: IDLE: Separate editor options from the general tab in config

[csabella]

Split the 'Editor Preferences' section of the General tab in configdialog into its own tab.

https://bugs.python.org/issue33051

[terryjreedy]

I am skimming through some of your open IDLE patches before quitting for the night. In particular, are there any that can/should be merged before 3.7.0c1 next Tuesday? This looks like a straightforward cut/paste with light editing. I still must look at dialog itself. If I like it, YES.

[csabella]

@terryjreedy I looked through the other open IDLE patches I have. Two of them have new tests for editor.py, so those would probably be too big to try to look at before Tuesday. I don't know if this is one you'd want to check before then - #5011.

[csabella]

Closing this was unintentional but I need to see if I can recreate the branch to reopen it.

Restored and rebased to master.

[vstinner]

I removed the " needs backport to 3.6" label, the 3.6 branch no longer accept bugfixes (only security fixes are accepted): https://devguide.python.org/#status-of-python-branches

[terryjreedy]

Closing as obsolete. init_validators was separately added and used on the existing GenPage. #26621 is a similar patch that separated windows preferences from Shell and Edit preferences. I did it after moving helplist to extensions tab and creating an ExtPage class. Moving indent spaces, #22954, completes the major changes we start around 3 years ago.