[ticket/11568] Use Goutte Client to install the board for functional tests

PHPBB3-11568
[ticket/11568] Set client manually so we can increase the cURL timeout

PHPBB3-11568
[ticket/11568] Any output before the doc type means there was an error

Change is needed to allow "Warning:" in the HTML body

PHPBB3-11568
[ticket/11568] Only use a static version of the client

PHPBB3-11568
[ticket/11568] Remove manual calls to assert_response_success()

PHPBB3-11568
[ticket/11568] Make CookieJar static aswell

PHPBB3-11568
[ticket/11568] Fix common_groups_test.php form handling

PHPBB3-11568
[ticket/11568] Trim the output to allow Tabs before INCLUDE overall_header

PHPBB3-11568
[ticket/11568] Allow different status codes

PHPBB3-11568
[ticket/11568] Add method to get page content

PHPBB3-11568
[ticket/11568] Only assert string when doctype is there at all

PHPBB3-11568
[ticket/11568] Remove unused method

PHPBB3-11568
[ticket/11568] Use static calls for static methods

PHPBB3-11568
[ticket/11568] Invert logic for asserting the response

PHPBB3-11568
[ticket/11568] Add comma at end of array key-value couple

PHPBB3-11568
[ticket/11568] Split status code and html debug assertion into two methods

PHPBB3-11568
Merge remote-tracking branch 'remotes/nickv/ticket/11568' into develop-olympus

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/11568:
  [ticket/11568] Split status code and html debug assertion into two methods
  [ticket/11568] Add comma at end of array key-value couple
  [ticket/11568] Invert logic for asserting the response
  [ticket/11568] Use static calls for static methods
  [ticket/11568] Remove unused method
  [ticket/11568] Only assert string when doctype is there at all
  [ticket/11568] Add method to get page content
  [ticket/11568] Allow different status codes
  [ticket/11568] Trim the output to allow Tabs before INCLUDE overall_header
  [ticket/11568] Fix common_groups_test.php form handling
  [ticket/11568] Make CookieJar static aswell
  [ticket/11568] Remove manual calls to assert_response_success()
  [ticket/11568] Only use a static version of the client
  [ticket/11568] Any output before the doc type means there was an error
  [ticket/11568] Set client manually so we can increase the cURL timeout
  [ticket/11568] Use Goutte Client to install the board for functional tests