aria2: Rewrite init script

* Add aria2 user and group.
* Use procd to start service.
* Add more supported options.

Compatible with previous version.

Signed-off-by: Hsing-Wang Liao <kuoruan@gmail.com>

net/aria2/files/aria2.conf

@@ -1,10 +1,31 @@
 
+# You can use most aria2 command-line options, replace '-' with '_'.
+# eg. 'rpc-secret' ==> 'rpc_secret'
+#
+# We do not support all options at this time. But you can add any option
+# with 'list extra_settings'.
+#
+# You can also add new config sections to define multi instance.
+#
 config aria2 'main'
 	option enabled '0'
-	option file_allocation 'none'
+	option user 'aria2'
+	option dir '/mnt/sda1/aria2'
+	option config_dir '/var/etc/aria2'
 	option bt_enable_lpd 'true'
 	option enable_dht 'true'
 	option follow_torrent 'true'
-	option user 'root'
-	option dir '/mnt/sda1/aria2'
+	option file_allocation 'none'
 	option save_session_interval '30'
+
+	# Add addition Headers here.
+	# eg. list header 'Content-Encoding: gzip'
+	list header ''
+
+	# Add BT trackers here.
+	# eg. list bt_tracker 'http://tracker.example.com/announce'
+	list bt_tracker ''
+
+	# Add extra settings here.
+	# eg. list extra_settings 'option=value'
+	list extra_settings ''