[ticket/12160] Add function to check if phpBB is installed.

PHPBB3-12160
[ticket/12160] Check if phpBB is installed before creating phpBB container.

PHPBB3-12160
[ticket/12160] Move phpbb_check_installation_exists() to functions_install.php

PHPBB3-12160
[ticket/12160] Use phpbb_check_installation_exists() in the other modules.

PHPBB3-12160
[ticket/9725] Create an Azure SQL compatible Schema

Two problems were encountered when installing on AzureSQL:
-Azure SQL does not support the ON clause of T-SQL
-Azure SQL requries a clustered index AKA primary key on all tables

The fix is makeshift; it introduces questionable primary indices, which should be replaced with auto--increment columns.

PHPBB3-9725
[ticket/9725] Add dummy indexes for Azure

SQL Azure requires a primary AKA clustered key on every table.
This adds a dummy INT column to act as key,
avoiding possible duplicate entries.
so that these columns can support bigger (speak: huge) tables

PHPBB3-9725
[ticket/11666] Removing MESSAGE_DELETED..

..in /en/posting.php as it is not used.

PHPBB3-11666
[ticket/12262] Also find vars array when it's defined in the trigger_event()

PHPBB3-12262
[ticket/12262] Fix location list for acp events with "Locations:"

PHPBB3-12262
[ticket/12268] Extension finder should not crawl through .git/ of extensions

This new filter ignores .svn and .git directories.
When searching for php classes and template files of extensions
we don't need to look inside these directories.

PHPBB3-12268
[ticket/12268] Use FilesystemIterator::SKIP_DOTS

PHPBB3-12268
[ticket/12268] Do not search in folders starting with a dot

PHPBB3-12268
[ticket/12268] Move class out of extension namespace and rename it

PHPBB3-12268
[ticket/12268] Rename class file to recursive_dot_prefix_filter_iterator.php

PHPBB3-12268
[ticket/12272] Fix hardcoded colons in subforums.

In subforums list, under the parent forum description, there are two
harcoded colons instead of {L_COLON}.

PHPBB3-12272
[ticket/12272] Fix hardcoded colons in subforums.

In subforums list, under the parent forum description, there are two
harcoded colons instead of {L_COLON}.

PHPBB3-12272
[ticket/12262] Do not use getExtension()

The method is php 5.3.6+ only.

PHPBB3-12262
[ticket/12262] Do not use inline assignments

PHPBB3-12262
Merge remote-tracking branch 'maelsoucaze/develop' into develop

* maelsoucaze/develop:
  [ticket/12272] Fix hardcoded colons in subforums.
  [ticket/12272] Fix hardcoded colons in subforums.
Merge pull request #2111 from nickvergessen/ticket/12262

[ticket/12262] Fix event exporter

* nickvergessen/ticket/12262:
  [ticket/12262] Do not use inline assignments
  [ticket/12262] Do not use getExtension()
  [ticket/12262] Fix location list for acp events with "Locations:"
  [ticket/12262] Also find vars array when it's defined in the trigger_event()