Require external gtest and remove it from submodules
Currently macOS requries the use of gtest external for some compilers. Lets make this change following the develop_joel update.
Probably should do the same for blosc?
Still need confirmation on how to install this directly on Linux through apt and have this all work.
Just for sake of making it clear - what is a reason to require external gtest (or blosc)? Is there any problem with having it as submodule?
It is a fair point, it may be un-necessary. But I have previously had various issues with compilation around gtest, that an external install seemed to solve.
Maybe one motivation is not suitable, its simply that blosc currently produces a bunch of warning, that during compilation produces a bit of noise.