Stop bundling the SAM modules/inverters database with pvlib

[Peque]

As suggested by @wholmgren.

A function could be used to download the files to a local hidden directory.

@cwhanse pointed out that the file may change upstream. I think we could use a URL that includes the commit hash (example) to avoid fetching the wrong version. Also, if you fear they may force-push changes and remove that reference, then I suggest you fork the project in pvlib.