As the possibility to test tags was introduced, some tests must me
adapated to work as before.
Tests that have to run at 'post_install' have to be tagged '-at_install'
and 'post_install'.
Also, nightly tests that contact external entities have to be tagged
'-standard' to avoid to be launched by default. Also they have to be
tagged 'external' so that they can be selected alone.
Contains the new ajax post function introduced by e8d58dd
in the community version of web that comes from mdo's
original code and that I was not able to get rid of.