introduce projects to group experiments

[sebkopf]

introduce the concept of projects or experiment groups to group experiments and make navigation easier e.g. when people need to set up many parallel chemostats but they're all part of the same project

in select boxes with experiment lists, selecting/deselecting a project/experiment_group then simply selects/deselects the entire set of experiments listed underneath

should this concept be called "project" or "experiment group"? it seems experiment group would be a bit more universal, not have quite as much implication as project