Show scrollbars only if needed

[vincentfretin]

This fixes #154

[mister-roboto]

@vincentfretin thanks for creating this Pull Request and help improve Plone!

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass.

Whenever you feel that the pull request is ready to be tested, either start all jenkins jobs pull requests by yourself, or simply add a comment in this pull request stating:

@jenkins-plone-org please run jobs

With this simple comment all the jobs will be started automatically.

Happy hacking!

[vincentfretin]

I fixed the rule controlpanels.plone.less and edited by hand barceloneta-compiled.css
I searched for instructions how to rebuild it but couldn't find them.
Do I need some upgrade step? I don't see my change in Plone.

[vincentfretin]

I probably didn't run the buildout after checkout plone.barceloneta it's ok now I see the change.

[vincentfretin]

I found out myself the commands to rebuild barceloneta-compiled.css and barceloneta-compiled.css.map, I added them in the README. If you made changes to the less files, to rebuild the files barceloneta-compiled.css and barceloneta-compiled.css.map you can execute this:

cd plonetheme.barceloneta/plonetheme/barceloneta/theme/less
npx lessc --source-map=barceloneta-compiled.css.map barceloneta.plone.local.less barceloneta-compiled.css

[vincentfretin]

I verified the sourcemap through chrome inspector, it works great and show the less files. It's even better than the previous sourcemap where the urls weren't correct.

[vincentfretin]

@jenkins-plone-org please run jobs