Emerge develop

[FJanssen-TNO]

Added id_mapping for carriers such that price profiles on carriers can be used.

It is not necessary to review the test case emerge and the revenue constraints as they will be changed, just check to ensure they don't break stuff.

Bugfixes on:

• esdl_heat_model information passing gas
• electrolyser using bigm for minimumload
• density calculations coolprop fixed pressure unit