Endian changes since formal review

• Both the endian types and endian conversion functions now support 32-bit (float) and 64-bit (double) floating point, as requested.
• Both the endian types and endian conversion functions now support UDTs, as requested.
• Both the endian types and endian conversion functions have been renamed, using a naming pattern that is consistent for both integer and floating point, and that emphasizes that aligned types are usually preferred compared to unaligned types which are deliberately given slightly uglier names.
• The conversion functions have been much revised, refactored, and otherwise improved based on review comments.
  • Both return-by-value and modify-in-place interfaces are provided, as requested.
  • Synonyms for the BSD byte swapping function names popularized by OS X and Linux are provided, so that that developers already used to these name can continue to use them if they wish.
  • In addition to the named-endianness functions, functions that perform compile-time (via template) and run-time (via function argument) dispatch are now provided, as requested.
• Compiler (Clang, GCC, VisualC++, etc.) intrinsics and built-in functions are used in the implementation where appropriate, as requested.
• For the endian types, the implementation uses the endian conversion functions, and thus the intrinsics, as requested.
• Headers have been renamed to endian/types.hpp and endian/conversion.hpp. Infrastructure file names changed accordingly.
• C++11 features such as noexcept are now used, while still supporting C++03 compilers.
• Acknowledgements have been updated.
• Headers have been reorganized to make them easier to read, with a synopsis at the front and implementation following, as requested.