What

• In the forms for users to sign in, create an accound, and edit parameters, we ask for / display the user id, but the field name is "username" or "user name", which is confusing (some users think they should enter their actual name). It would be clearer to name that field "user id".

Code pointers

Needed:
in po/common/common.pot and po/common/en.po:

• change all the stringids that contain username / user_name to contain user_id instead
• change those string values to use "user id" instead of "username" or "user name".