Model table - add short description

[Avsecz]

@akundaje suggested

looking at the models page, I realized that it would be helpful and more accessible to have a one-liner description column in the model group table. Otherwise its very difficult to parse from the current information what a model is doing. In other words, a user explicitly looking for a specific model might find one but if someone is just browsing, its impossible to know what the model groups actually represent. The Tags column is useful but those are just short words/tags. I am suggesting complementing it with a one-liner (with a word limit) free-text description for model groups. E.g. For DeepBind model group a sample one-liner would read something like "Neural network models mapping regulatory DNA sequence inputs to binary predictions of in vivo transcription factor binding". If the search could index the free text that provides a more free-form strategy for searching for relevant models beyond the tags.