Add session storage information tab

[jasperdcbe]

It would probably be useful to have an extra tab with session storage information, following session storage engines could be defined: file, memcached, redis, database

The data size + amount of sessions in the current storage could also be listed, because on some servers this causes issues when session.gc_probability is set to 0.

Does anyone else think this could be a useful addition? Feedback?

[edannenberg]

+1, think it would be enough to just do it in a widget inside the cachestat tab though. Either way, adding new tabs with some widgets of some sort is pretty straight forward now.

[sylvainraye]

+1 too and as had written @edannenberg will be preferable to be located in the existing tab Cache Statistics, just add it under the existing cache information. Those are displayed only if they are available. So a new tab doesn't make sense. If you wish to do it you are welcome. Please push to develop branch

thanks for your contribution

[edannenberg]

Might be even more fitting to put it into system overview tab below the magento info widget.