Removing filters re-loads other filters

[will-moore]

From #27 (comment)
Each time a filter is removed the key_value pairs are reloaded and UI regenerated
Example:

• Add ROI_count
• Add Key_value. wait for the UI to be built
• Remove ROI_count
• The Key_value component will be rebuilt.

[will-moore]

This bug is not just for map_annotations, but will show up anytime you remove a filter (except for removing the last filter in the list).
This is because the key that tells React whether each filter is a new vv existing component is based on the name and Index.

<ParadeFilter
    key={fname + idx}

So, React will re-load filters if the index changes, which includes re-loading the filter and data from OMERO.

Kinda tricky to think how to fix that since you may have several filters with the same name e.g. Tag and a different Tag selected in each. If you remove one of them, we want React to remove just that one and not change the others. But it's hard to see how we can define a key for each filter based on the current state of each filter.