[FEATURE] add keepParameter option for domains

[fvosberg]

if you are using 2 domains for 3 languages, you need to have the L parameter present for the pagepath. Now you have a keepParameter option for the _DOMAINS configuration, to prevent realurl from unsetting the lang param.

Example:

foobar.de/de/ foobar.de/en/ foobar.es

If you configure the _DOMAINS you loose the language param for page path decoding. To prevent this and leave the API backwards compatible, I've introduced a new option for the _DOMAINS section.

[dmitryd]

If you configure the _DOMAINS you loose the language param for page path decoding

No, you do not. Path decoding only uses language variable. It is set here and later used at path decoding.

To prevent this and leave the API backwards compatible, I've introduced a new option for the _DOMAINS section.

"The API" for realurl does not exist. And realurl always removed that var. So there is nothing about compatibility here.