[ticket/10896] Adds email validation to email settings in ACP

Adds a new validation type to the ACP validate_config_vars function
and implements it on the board_contact and board_email settings.

PHPBB3-10896
[ticket/10896] Move EMAIL_INVALID_EMAIL to common, replace EMAIL_INVALID

PHPBB3-10896
[ticket/11361] Make sure that array passed to strtr() has the proper format.

The array $date_cache[$format]['lang'] passed to strtr() contains a sub-array
which results in an E_NOTICE being thrown for 'Array to string conversion' on
PHP 5.4.
Ensure that the array passed to strtr() is one-dimensional by filtering out
non-string values.

PHPBB3-11361
[ticket/11122] Add EXreaction to docs/AUTHORS.

PHPBB3-11122
[ticket/11122] Move rxu to 'Former Contributors' section.

PHPBB3-11122
[ticket/7262] Backport set_config() and set_config_count() docs from develop.

PHPBB3-7262
[ticket/7262] Add $is_dynamic example to set_config() and set_config_count().

The logic is the other way around here in comparison to develop's
phpbb_config_db class, so add examples to make things more clear.

PHPBB3-7262
[ticket/7262] Add note about set_config() not updating is_dynamic.

PHPBB3-7262
Merge remote-tracking branch 'github-bantu/ticket/7262' into develop-olympus

* github-bantu/ticket/7262:
  [ticket/7262] Add note about set_config() not updating is_dynamic.
  [ticket/7262] Add $is_dynamic example to set_config() and set_config_count().
  [ticket/7262] Backport set_config() and set_config_count() docs from develop.
Merge remote-tracking branch 'github-bantu/ticket/11122' into develop-olympus

* github-bantu/ticket/11122:
  [ticket/11122] Move rxu to 'Former Contributors' section.
  [ticket/11122] Add EXreaction to docs/AUTHORS.
Merge remote-tracking branch 'github-exreaction/ticket/10896' into develop-olympus

* github-exreaction/ticket/10896:
  [ticket/10896] Move EMAIL_INVALID_EMAIL to common, replace EMAIL_INVALID
  [ticket/10896] Adds email validation to email settings in ACP
Merge remote-tracking branch 'github-bantu/ticket/11361' into develop-olympus

* github-bantu/ticket/11361:
  [ticket/11361] Make sure that array passed to strtr() has the proper format.
[ticket/11355] Wrong error message when no user is selected.

In ACP group membership management, if you select 'remove member
from group' without selecting any users and submit,it will display
a wrong error after confirmbox. Since no users are selected, this
should not go even until confirmbox. Added a new condition to check
weather any users are selected when the action is 'deleteusers'
in acp_groups.php and disply a correct error.

PHPBB3-11355
[ticket/11355] Referred proper variable when validating selection.

Earlier PR was referring wrong variable $name_ary. Changed it to
$mark_ary which actually contains selected user ids.

PHPBB3-11355
Merge branch 'ticket/11355' into develop-olympus

* ticket/11355:
  [ticket/11355] Referred proper variable when validating selection.
  [ticket/11355] Wrong error message when no user is selected.
[ticket/11358] Success message even without selecting a user.

In group membership management, if you perform the action
'Make group default for member' without selecting any user,
a confirm box will be displayed and will show a success
message after confirming. Added a new condition to fix this
issue in acp_groups.php. It will check weather any users are
selected before performing above action.

PHPBB3-11358
[ticket/11358] Removed redundant code and referred proper variable.

Error was thrown when no users are selected before executing the code
chunk which manually adds all the user to make the group default.
Removed this code and referred $mark_ary instead of $name_ary which
will not have selected user ids.

PHPBB3-11358
[ticket/11358] Enabled link making all users default for a group.

Detect whether link is clicked or form is posted for making users
default for a group. If form is posted and no users are selected,
validation happens and displays an error message. When the link is
clicked, all the users will be default users for that group.

PHPBB3-11358
[ticket/11358] Changed the action parameter value to represent the link.

Changed the action parameter value to recognize whether 'Make default
group for every member' is clicked. If so execute a seperate code block
under switch statement for $action and add all the users as default
for the group.

PHPBB3-11358
[ticket/11358] Changed the name of post parameter.

Replaced the parameter name 'defaultbylink' to a meaningful name
'set_default_on_all'. Parameter is used for making all users
default for selected group in acp_groups.php.

PHPBB3-11358