Add HTTP/2 support to nginx build and enable it in nginx.conf

docker/main/build_nginx.sh

@@ -60,6 +60,7 @@ cd /tmp/nginx
     --with-file-aio \
     --with-http_sub_module \
     --with-http_ssl_module \
+    --with-http_v2_module \
     --with-threads \
     --add-module=../nginx-vod-module \
     --add-module=../nginx-secure-token-module \

docker/main/rootfs/usr/local/nginx/conf/nginx.conf

@@ -55,6 +55,8 @@ http {
     server {
         listen 5000;
 
+        http2 on;
+
         # vod settings
         vod_base_url '';
         vod_segments_base_url '';