fix(webui:prefix) to support play.http.context change

[vladshub]

Support plays framework play.http.context which allows use of different base path for example tools.example.com/broccoli as base path and the api requests should go to /broccoli/api/v1

fixes #368

[FRosner]

Thank you for this contribution! Did you succeed to modify the base path after this change?

[FRosner]

Is it working for you with the change implemented, @vladshub?

[vladshub]

Hi @FRosner I was away for a long weekend and just now got back to it... Testing it now and by the end of day will give you an answer :+1:

[FRosner]

No worries @vladshub! Just let me know as soon as you succeeded :)