remove strings that do not need translation from translation files before sending to weblate

We have a limit for strings in weblate for the free service, and we send a lot of strings to translate that are not to be translated (commands, snippets of logs...)

we can make sure that this strings do not even arrive to weblate:

• compiling a .pot file with the strings that we dont want (ignore.pot)
  • community portal
  • support portal
  • tb manual
  • tpo
• using it with:
  • msgattrib -i contents.pot --set-obsolete --only-file=ignore.pot -o contents.pot
• fix the check_po status job that counts translation in lektor builds, otherwise it will report read-only strings as new strings needing translation
• document all this