Discuss how we want to deal with inside / outside coating materials

[vpicavet]

At some point we would like to handle inside / outside coating materials. This would need some additional tables to the qwat/qwat-data-model and some configuration to setup the forms.

[vpicavet]

First step is to design what we want to handle. Then issue #95 is for implementation.

[haubourg]

Postponing this to End 2018, should be inlined with the potential rework for a full SIA compatibility, which could be a 1.4 target for QWAT