edit multiple resources at once

[lsteinmann]

it should be possible to modify the editing modal to support editing multiple resources at once. this would happen by selecting multiple resources, right clicking, then selecting 'edit'.

if I remember correctly, the plan was this: differing values will just not be displayed / displayed as 'differing values' or similar, since it is not feasible for more than a few resources; instead, one gets the option of selecting values for fields that will then be updated in all selected resources, disregarding the information saved beforehand.