Adds collapse to child columns

[garbast]

With this change it is possible to collapse each child column
individually and adds configuration to container definition
with which it is possible to define, which column should be
collapsed by default.

Resolves: #123

[larsgoo]

Thanks for your work @garbast ! We are using this in an in-development project and so far I've only gotten positive feedback, everything seems to work as intended. Hope this finds its way into a future container release - Working with nested accordions does no longer give our editors a headache :D

[garbast]

Ping. Can we get any traction on this pull request?

[achimfritz]

i would suggest to not include this Feature in EXT:container, but provide a new Extension (e.g. EXT:collapsible_container) which can be used if needed by Integrators easily.

This is my Suggest:

Provide JS, HTML and CSS Code in this Extension

Integrators can simply modify Grid Layout/Templates/Partial Paths when register container (s. https://github.com/b13/container/blob/master/README.md#methods-of-the-containerconfiguration-object (setGridTemplate, setGridPartialPaths, addGridPartialPath, setGridLayoutPaths)) and use "collapsible_container" Extension.

The Code-Base of EXT:container should be keeped Small, and focus more on Stablity than on Features. Features or Custom Requirements can be provided by Site Extension or by other Extensions (i did already anything crazy stuff you cannot imaging)

Thanks for your work, and please put it into an own Extension (ask me if anything is missing)

[evoWeb]

The problem is, that it isn't done by just adding some frontend files. The ContainerGridColumn and the ContainerPreviewRenderer need to be modified too.

ContainerGridColumn needs to be modified to be able to define if container are collapsed by default.

ContainerPreviewRenderer need to be modified to respect users previous choice of collapsing and un-collapsing a container.

Cant we agree, that this are modifications worth merging?