[ticket/12413] Tests: Adding functional tests for the feeds

Some tests are disabled until PHPBB3-12418 (#2331) and PHPBB3-12421 (#2330) are
fixed and merged

PHPBB3-12413
[ticket/12413] Useing @depends to transmit the state of the board

the state of the board is calculate in the first test and transmit to the
others thanks to the @depends annotation.

PHPBB3-12413
[ticket/12413] Using static attribute instead of @depends

Using a static attribute to store the initial state of the feeds instead
of transmit it with the @depends annotation.

This attribute is also added to backupStaticAttributesBlackList

PHPBB3-12413
[ticket/12413] Adding the missing visibilities

PHPBB3-12413
[ticket/12413] Fixing the failed test

The test was failing because travis is too fast: 2 posts had the same
timestamp.

PHPBB3-12413
[ticket/12413] Fix: coding style

PHPBB3-12413
[ticket/12413] Fix coding style

PHPBB3-12413
[ticket/12413] Coding style again

PHPBB3-12413
[ticket/12413] Move parent:open() call to the end of the function

PHPBB3-12413
[ticket/12413] Disabled unapproved and solftdeleted tests

PHPBB3-12413