Improve the accuracy and privacy of the search results

[rafaehlers]

This requires #1753

There are two main problems with GravityView's search functionality that prevent some specific use cases that require data privacy:

1. It's not easy to search for exact matches. The famous "Kansas/Arkansas" search problem. We usually had to resort to two code snippets to achieve that: https://github.com/GravityKit/gv-snippets/branches/all?query=exact
2. There's no way (without using custom jQuery code) to require fields on the search bar.

With these two problems, you can't create a View that hides entries unless a search for an exact match in two or more fields is performed.

Here's a video explaining this: https://www.loom.com/share/f8dd90724f5e46b0bf3e407130675f13

My suggestion is to add two additional settings in the Search Bar:

1. Only search for exact matches (this should be a per-field setting)
2. Make fields required (another per-field setting)

[zackkatz]

Related #1753 #1174 #1913 #921