Fix erase timeouts, atxmega16c4 follow-up, target listing, changelog, progress output

There are several items in this request. The main one is to improve the behaviour of erase on some chips where the bootloader returns a busy status rather than waiting for the erase to complete before returning status.

The next is a follow-up to Olivier Pisano's pull request which added support for the atxmega16c4. This corrects the bootloader size and adds the sister chip atxmega32c4. It also adds these to the documentation.

The target listing has been rewritten to group by processor type and there are now options to output in tex or html format to simplify doc updates.

The news and changelog files have been merged to produce changelog.txt

The progress output has fewer words in UPPERCASE