Use inline source maps for karma

Merged Winnie Hellmann requested to merge winh-karma-sourcemaps into master

What does this MR do?

Add inline source maps to the webpack config when running with Karma.

Why was this MR needed?

Source maps were only enabled for production and dev environment but Karma was neither of those.

Screenshots

Before

Screen_Shot_2017-05-31_at_11.42.09

After

Screen_Shot_2017-05-31_at_11.39.54

Related issues

closes #30996 (closed)

Edited by Winnie Hellmann