Description of problem:
When you create a new project or version and configure languages, I need to delete one by one to just leave the necessary language(s).
It is often one or two only and it takes a long time to remove them, especially in zanata.org. It would be helpful if I am able to select all language and remove, then add necessary one(s) only.
Version-Release number of selected component (if applicable): 3.5
How reproducible: 100%
Steps to Reproduce:
1. Create a new project in Zanata
2. Click Settings and then select Languages tab.
3. Check the default list.
4. Try to set single language.
It requires to remove unnecessary languages from the list one by one.
It should allow to start from zero.