remove docker files for PHP 5.6

docker/dev/mtt-php56-apache/Dockerfile

@@ -1,6 +0,0 @@
-
-FROM php:5.6-apache
-
-RUN docker-php-ext-install mysqli opcache && \
-	rm -f /usr/local/etc/php/conf.d/docker-php-ext-opcache.ini && \
-	mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"

docker/dev/mtt-php56-apache/docker-compose.yml

@@ -1,14 +0,0 @@
-version: '3'
-services:
-  web:
-    build: ./
-    image: mytinytodo-dev:php5.6-apache
-    container_name: mtt-dev-php56-apache
-    ports:
-    - "8080:80"
-    environment:
-    - MTT_ENABLE_DEBUG=YES
-    volumes:
-    - ../../../src:/var/www/html
-    - ./php-mtt.ini:/usr/local/etc/php/conf.d/php-mtt.ini
-    - ./php-opcache.ini:/usr/local/etc/php/conf.d/php-opcache.ini

docker/dev/mtt-php56-apache/php-mtt.ini

@@ -1,7 +0,0 @@
-
-; Since PHP 5.4 E_STRICT is included in E_ALL
-error_reporting = E_ALL
-
-log_errors = On
-display_errors = On
-display_startup_errors = On

docker/dev/mtt-php56-apache/php-opcache.ini

@@ -1,34 +0,0 @@
-;; opcache.ini
-
-;; check /usr/local/etc/php/conf.d if exists docker-php-ext-opcache.ini
-
-; To disable opcache just comment this line
-zend_extension=opcache.so
-
-[opcache]
-opcache.enable=0
-opcache.enable_cli=0
-
-; The size of the shared memory storage used by OPcache, in megabytes. The minimum permissible value is "8", which is enforced if a smaller value is set.
-; Default is 128.
-opcache.memory_consumption=128
-
-; The maximum number of keys (and therefore scripts) in the OPcache hash table.
-; The actual value used will be the first number in the set of prime numbers
-;  { 223, 463, 983, 1979, 3907, 7963, 16229, 32531, 65407, 130987, 262237, 524521, 1048793 }
-;  that is greater than or equal to the configured value.
-; The minimum value is 200. The maximum value is 1000000. Values outside of this range are clamped to the permissible range.
-; Default is 10000.
-opcache.max_accelerated_files=1000
-
-; How often to check script timestamps for updates, in seconds. 0 will result in OPcache checking for updates on every request.
-; This configuration directive is ignored if opcache.validate_timestamps is disabled.
-; Default is 2.
-opcache.revalidate_freq=2
-
-; If enabled, OPcache will check for updated scripts every opcache.revalidate_freq seconds.
-; When this directive is disabled, you must reset OPcache manually via opcache_reset(), opcache_invalidate()
-;  or by restarting the Web server for changes to the filesystem to take effect.
-; Default is 1.
-;; Override in docker-compose
-opcache.validate_timestamps=1