Allow unmarking pages from translation

Previously this was only possible for "broken" pages. Now also for
active ones: the system automatically removes any translate tags,
section markers and languages tag.

Added some styling to the success/error/warning messages so that
they are more visible and added page listings on some errors pages
for usability.

Fixed completely wrong documentation for getSourcePageText and
used correct title for makeContent.

Change-Id: Id1a7bb136bef24b9a8a5041422c47fca5bb9cd43
Merge "Allow unmarking pages from translation"