Improve search / filter

[TrystanLea]

Improve the search / filter feature, some column values are dont seem to be working with the feature. Explore ways to filter by a stats value e.g flowT<30.

[kamilfb]

Hi @TrystanLea @glynhudson I've implemented enhancements to the table filtering (system_list.php) by adding support for new operators: #69.

Also, I've added a simple side panel to add/edit/view the filter: #70. Still work in progress, but very keen to get your feedback.