Bug 578309: Tidy up documentation HTML files

First chunk of tidied files.
All these have been cleanup up with HTML tidy with the "-miq" option.

Change-Id: I86084b7dfc5edef95b3cda6e347650ea9d98502a
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.common/+/189881
Tested-by: Matthias Becker <ma.becker@sap.com>
Reviewed-by: Matthias Becker <ma.becker@sap.com>