Add a "Searching..." bar or text when search is ongoing

[mestaki]

Reproduce the issue:
From the main "View Studies" page, search for a term like "Paulus". It takes about ~7-10 seconds for the page to start showing the results, during which time no indication is made that search is ongoing. This leads to user thinking the search has returned 0 results and they move on to the next search item before the previous search is complete. I suspect this issue will become exaggerated as more data is added and searches take longer.

Propose behavior:

1. Show a "Loading" bar or text when a search is still ongoing, or
2. Add a "Search" button beside the search field that users click that goes dim when a search is ongoing.

[antgonza]

@mestaki; thank you for your suggestion - you are right about time and what's going on in the system. As an example, I added a 5 second delay in my local test to simulate what's going on; basically, if you type something that you expect datatables says is not found because the list hasn't being loaded, like this:

As you suggested, there is an option in datatables that will show that the data is being processed (downloading) which is basically a little frame on top of the other messages, like this:
.

Will this work? Anyway, here is the PR in case you have specific suggestions about language.

[mestaki]

Hey @antgonza,
Awesome this is perfect! Glad it wasn't too much of a hassle to change :)

[antgonza]

Thank you for your feedback and review - this will be deployed during this cycle (in a few weeks).