TODO: link wiki:piuparts/UseCases||UsageTips in README_1st (after we agreed on a name)

Signed-off-by: Holger Levsen <holger@layer-acht.org>
htdocs/index.tpl: Further restructure 'about p.d.o' section

Signed-off-by: Holger Levsen <holger@layer-acht.org>
htdocs/index.tpl: improve grammar in 'about p.d.o'

Signed-off-by: Holger Levsen <holger@layer-acht.org>
htdocs/index.tpl: use <em> instead of <i>
htdocs/index.tpl: sed s# to be run##
When distro defaults are explicitly specified, use the distro default mirrors (Closes: #710347).
debian/changelog: Add Closes: for #662633