[ticket/9758] Adds global template variable CURRENT_USER_AVATAR

PHPBB3-9758
[ticket/9758] Changes class name of new "span" in overall_header.html

PHPBB3-9758
[ticket/9758] Removed useless if-conditions to include functions.php

PHPBB3-9758
[ticket/9758] Error because of missing functions_display.php fixed

PHPBB3-9758
[ticket/9758] Optimises the html code of avatar image in header

PHPBB3-9758
[ticket/9758] Fixed bug in mcp_warn.php

PHPBB3-9758
[ticket/9758] Adding impr. for overall_header display of avatar and username

PHPBB3-9758
[ticket/9758] Removed the needless space after first ENDIF

PHPBB3-9758
[ticket/9758] Adds id and changes filter to fix travis CI test

PHPBB3-9758
[ticket/9758] Slims the line 4775 in includes/functions.php

PHPBB3-9758
[ticket/9758] Remove unnessary if-question for include functions_display

PHPBB3-9758
[ticket/11459] Add a migration/schema_generator

It loops over the migrations and creates the schema from it.

PHPBB3-11459
[ticket/11459] Add Schema from 3.0.0

PHPBB3-11459
[ticket/11459] Use new migration/schema_generator to create schema files

PHPBB3-11459
[ticket/11459] Update schema files with new script

The order of some tables and columns was changed

PHPBB3-11459
[ticket/11459] Remove old schema file

PHPBB3-11459
[ticket/11459] Update doc blocks

PHPBB3-11459
[ticket/11459] Add migration for migrations table

This migration will always be skipped on updates, because database_update.php
creates the table. But the create schema script requires the migration,
so the table is created for new installs.

PHPBB3-11459
[ticket/11459] Correctly handle index column length

Code is copied from db\tools::sql_create_index()

PHPBB3-11459
[ticket/11459] Remove spaces from the end of lines in MSSQL

PHPBB3-11459