missing import_key field, ref generator parameter must be task not
project, import must use css, serious database integrity problem
accepting duplicate tasks.

(sometimes we need, sometimes not).

Close #4813

As is not the branch develop, instead of transifex, we use GIT

Conflicts:
	htdocs/core/class/html.formprojet.class.php

tolerance parameter)

remove around 50 duplicates.

modules

Fix: visible list of tasks are for opened project only.