Add option to set log file location or disable logging

[EdiWang]

你的功能请求是否与一个问题有关？请描述。 I put v2rayN in my OneDrive in order to sync across my PCs with config files. However, every time I use v2rayN on any machine, it creates log files, which would also sync to OneDrive. Sometimes it will make conflict because the log file are using date as filename, which is identical on 2 or more machines.

描述你希望的解决方案

Add option to turn off logging.

描述你所考虑的替代方案

Add option to let user change log file location. e.g. User directory, temp folder, etc...