Add allinone (clean/vendor/build) default target to Makefile, Remove gui/providers/providers.json from git repo, Don't use unlink on *nix in Makefile

Fixes #867 (closed)

Makes developing a bit easier.

I removed the auto-generated providers.json from the repo. It seems like git also removed the upper directory. Seems like there was nothing else inside.... Nevermind: I had to change the gen-providersjson python script to create the directory....