Added JqGrid groupingView including example

[webdevilopers]

Fixes issue #108

JqGrid groupingView example URL:
http://YOUR-PROJECT//zfcDatagrid/jqgrid/groupingview

This PR will not add groupingView as a new feature itself. It simply adds an example that shows how to set groupingView to an individual layout.

The example is based on the JqGrid demo:
http://trirand.com/blog/jqgrid/jqgrid.html - Grouping - Grouping row(s) collapsed

The important part is the Renderer that has been changed in order to allow sorting when using groupingView.

There are some differences in the behaviour of the ZfcDatagrid example and the JqGrid example when you use sorting Inv No or Date. But this should be checked later since it is no "bug".

[webdevilopers]

@ThaDafinser Can you explain what the FAIL means? Is there an conflict between my and other commits?

[ThaDafinser]

@webdevilopers its because of the psr-2 standard, see here:
https://travis-ci.org/ThaDafinser/ZfcDatagrid/jobs/27767005#L140

Can you fix this maybe? You do it with this tool: fabpot/php-cs-fixer

[webdevilopers]

I'm beginning to understand what this Travis thing is actually about.
I will check it out in the next weeks and fix it, @ThaDafinser !

[ThaDafinser]

@webdevilopers i started with Travis also with this project.
It's just amazing.

The PSR-2 thing i started some time ago ....a lot of benefits:

• no different formatting anymore
• better diffs
• ...

[webdevilopers]

I will wait for #97 .

[ThaDafinser]

Like already thought in the other PR, i think it would not be good to only include such a feature for one renderer.

At least the export renderer would need to be able to achieve the same.

If you have an idea how we can achieve this, feel free to reopen this PR