Adds _search query parameter

[djperrefort]

Adds ability to perform general searches via the _search parameter. Two design choices to note:

1. I've generally excluded boolean and time fields from the search. Since these values have a limited set/range of values, I find them less useful to include in a search.
2. I've prefixed the query parameter with an underscore to avoid possible naming conflicts with query parameters that map to model fields. As an extension of this. I'm thinking of also renaming the ordering argument to _ordering.

[Comeani]

I've taken a look at this and it generally looks good, and I think what you said about ordering makes sense. Right now were are using a filters parameter in the client to do a similar thing, but it appears to be stricter (looking for exact matches to the provided value, for example). Is the intention of this primarily to broaden the behavior to include prefixes for more advanced search like regex, contains, starts-with, etc. ?

[Comeani]

Yassin is answering my question now, adding detail about shifting the responsibility for the search from the client to the server.

[Comeani]

Looks good to me, lets chat about any corresponding changes to how the client's factory methods get what they need from the server when this is in place.