Manual translations import is too obscure

[Märt Põder]

The guidelines are too general and not really clear.

https://help.launchpad.net/Translations/YourProject/ImportPolicy and the message before uploading (including popup) give contradicting instructions:

* It is not clear whether the directory structure for tarballs is "recommended" or given as "an example" (and as an example in what sense).
* It is not clear what is meant by .pot file not containing message IDs and at the same time msgid containing English strings.
* It is not clear whether translations are imported in couple of hours or couple of days and what are the precise reasons for the differences in import time.

This makes it really annoying to upload translations (especially the first time), because users do not have any clue if the import is delayed because they have presented data in an unacceptable shape or it is just delayed because of human factor. If the automatic import does not seem to work, users try to reshape the data and reupload and waste lot of time/energy for nothing.