Appveyor test failed with

"Traceback (most recent call last):
File "C:\projects\cpython\lib\idlelib\idle_test\test_configdialog.py", line 79, in test_bold_toggle
d.bold_toggle.toggle()
AttributeError: 'ConfigDialog' object has no attribute 'bold_toggle'"

Indeed it does not, as I forgot to add 'self.' in front of of the definition to save the reference. How did this pass travis -- by not runnig gui tests. Easy fix for3.7 first, but exposes another problem.

"FAIL: test_set_samples (idlelib.idle_test.test_configdialog.FontTabTest)

Traceback (most recent call last):
File "C:\projects\cpython\lib\idlelib\idle_test\test_configdialog.py", line 90, in test_set_samples
self.assertTrue(d.font_sample == d.highlight_sample == expected)
AssertionError: False is not true"

This might be an issue with the number 5 versus string '5', but should not be different on Win7.

I disabled test class on master until I fix it properly.

Add to message:
Verify that clicking the bold checkbutton and calling its command, set_samples, changes the bold setting of both samples. Simplify some names in configdialog.

Incorporates changes and fixes from PRs 2798 and 2810.