Moved container class to layout

[bodrak]

Moved the container class (bootstrap) into the layout template. It makes more sense for two reasons:

1. Code optimization: As the 3 templates extending the layout (overview, new and grid) are adding this class, it is optimized to put it only on the layout template.
2. For a better integration with backends, where there often is a sidebar on the left, the container class breaks near the breakpoints, and so we can more easily fix it by replacing this class by a container-fluid class by example.

Most of the changes are indents.