Multigene curator - various improvements

[adkinsrs]

• In the gene selection section, if the user hits "Clear all genes", the manual gene entry is not cleared.
• Heatmap memory issues still seems to persist in some datasets where clustering is disabled and there is no filtering of observations.
• Find some way to catch the OOM error and propagate it.
• I noticed that with the heatmap, it seems that it ran out of memory before mapping genes (because the observation filtering step is before it). This lead to some confusion where only one gene mapped to the dataset and that error should have been thrown. For cases where only 1 gene maps to the dataset, I need to verify the proper error is being thrown instead of a generic catch-all error.
• Perform some orthology mapping before plotting. This can either be after the user switches focus off of selecting genes, or before the plotting itself (where we can pass in the orthologs instead of the queried genes). This would let us assess if we have the requisite genes before the plotting API call checks it.