Inherit from base webpack config

[alexrobin]

Test configuring applications by inheriting from a base webpack config rather than reconfiguring everything in each app.

See https://gist.github.com/ericclemmons/40a2783313d157d8b448

[mdhsl]

The problem is that what seems to be the most complicated in the webpack conf is the use of cesium which requires a particular configuration. But this configuration can't be put in a 'basic' webpack file because it depends on the cesium lib. And it's not better to force users to install the cesium lib for all applications. This difficulty is related to cesium itself and not to OSH.

For the rest, it is possible to make a very basic conf file but there will be almost nothing in it. The webpack file reflects the state of the application in debug/production mode, it is often specific to it.

Another problem is the use of loaders, many loaders are in conflicts, there are several types of loader for example by file. For example, in our applications, we use style-loader associated with css-loader while other basic applications use url-loader instead. If someone inherits this conf file with a loader that is incompatible, this generates conflicts, and to have experienced it, the error is never explicit, it is often difficult to know that it is a conflict between loader. In the end, I have the impression that inheriting a conf file could cause more problems than solving them