Change plugin id from 'v2ray' to 'v2ray-plugin' for consistency

#13 was closed without any comments so I opened another one.

[Mygod]

Maybe but this would introduce problems with existing profiles.

[CzBiX]

@Mygod How about add a feature to support plugin alias, or just convert it when read profiles field.

[Mygod]

@CzBiX Good idea. We can support an IS_ALIAS metadata.

[CzBiX]

When user import profile from QRcode that generated on other platform, or when SIP008 becomes popular, this issue will be big problem.