lib: add console.{group,groupCollapsed,groupEnd}()
Implements nested console groups. This improves code portability by matching with console object standard proposal and major browsers console API.
console.group()
console.groupCollapsed()
console.groupEnd()
Notes:
- Starting a new group prefixes each line of output with two-spaces per group/indent level.
- console API documentation is updated to include new functions.
- Test case
test-console-group.js
is included.
(This is resubmit of #1727 to replace invalid source branch)