luci-app-aria2: Refactor, new views and more options

This commit contains:

* Refactor package code.
* Add options for RPC, HTTP/HTTPS and BT.
* Improve descriptions for some options.
* New views for config files and log files.
* Also updated translation for simplified Chinese.

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