Use two Dockerfiles, move Docker stuff to /docker

docker/php/custom.ini

@@ -0,0 +1,15 @@
+; based on https://github.com/dead-guru/devichan/blob/master/php-fpm/custom.ini
+
+memory_limit = 2G
+max_execution_time = 30
+upload_max_filesize = 2G
+post_max_size = 2G
+pm = dynamic
+pm.max_children = 20
+pm.start_servers = 5
+pm.min_spare_servers = 3
+pm.max_spare_servers = 10
+
+extension = igbinary.so
+extension = redis.so
+extension = imagick.so