Prep SWFFT-GPU for usable release

• Formatted code with clang-format with a style based on LLVM.
• Refactored some of the code, moving implementations into header files for small classes.
• Simplified and reduced lines of code by using more inheritance.
• Began documenting code with simple doxygen comments (also added docs/Doxyfile to auto generate documentation).
• Added two more bashrc scripts (untested!)
• Updated readme.
• Removed the GPU delegate backend - it wasn't super useful and needed special methods like synchronize() which the other backends do not.
• Refactored make build system - should be easier to work with now.
• Reorganized include directory.
• Generally cleaned stuff up.