Massive change to use of locations and calculation of production volumes

[cmutel]

Highlights:

• Links market groups
• RoW is now resolved in space for both consumers and suppliers
• Added constructive_geometries as base source of data
• Track both gross and net production volumes or markets and transforming activities

Fixes #20, #149, #143, #100, and #92.

Note that there are still serious questions with how the release version of ecoinvent actually works, including #147 and #140.

Before merging, need to add the following validation and logging functions: #131, #148, #150, #151.

[coveralls]

Coverage increased (+0.05%) to 86.928% when pulling 9d11684c8e8a7d19edbd49ed2a7688660db074da on market_groups into 7e80484d48c6c733f890e0e90de762fabd3037c7 on master.

[cmutel]

Also fixes #140.