hardcoded base url for collections in dts api

[balmas]

the use of localhost:5000 as the base url for the DTS collections seems to be hardcoded
this is in the dts-draft-1 branch

[PonteIneptique]

This is a good bug where a decision needs to be taken : do we want relative URIs or do we want to simply force people to enter app["SERVER_NAME "] ?

[balmas]

ah, well you know what my answer is going to be. A nice default (i.e relative URIs) and the ability to override with a setting.

[PonteIneptique]

Untested (neither unit or dev server) version on 753a61f