CMake fix

[jatkinson1000]

I believe this closes #14

Namely the comments below the main one regarding install location.
cmake files are now placed at $CMAKE_INSTALL_PREFIX/lib/cmake/FTorch/ allowing CMake to locate things automatically if passed CMAKE_PREFIX_PATH = $CMAKE_INSTALL_PREFIX.

This means we no longer specify the FTorch_DIR argument, instead using CMAKE_PREFIX_PATH as standard.

Regarding the other items in #14:

• Documentation has no dependencies as it is deployed by a GitHub action
• Examples exist as standalone items with their own CMake - I would argue that they should not in any way be combined with the main CMakeLists
• Currently no testing dependencies (or testing 😬) but we can make this a flag option when we write them.

Tested on apple M1 mac to build library, install, and build/run examples 1 and 2.
Would appreciate someone else replicating on a different system.

[ElliottKasoar]

Both examples seem to work for me on WSL (Ubuntu 20.04)

I assume we're not updating the work-in-progress example for now?

Worth noting we'll need to update the benchmarking repo too.

[SimonClifford]

Not sure about glob patterns in LDFLAGS suggestions in README.md

[TomMelt]

looks good but not happy with *

[jatkinson1000]

OK, made everything /lib and added a note about alternatives.
If someone can green-light I'll merge.