* added configuration support to the build script (everything is now enabled by default, flags to disable are --no-cuda, --no-opencl and --no-openal)
 * added a new configuration header (floor/floor_conf.hpp), this is now used instead of compiler flags/defines everywhere (a default header with everything enabled exists, but it can/will be overwritten by any changes made via build.sh); for consistency, this also applies to the xcode project (removed all flags there)!
 * added new core/essentials.hpp header that has no external header dependencies and handles misc compiler/conf/system defines/macros (this is (1) used in all opencl/cuda/openal headers now to query if the resp. feature/lib is enabled or not, and (2) used in several headers instead of core/platform.hpp now); note that this header now contains parts from cpp_headers.hpp and platform.hpp that have been removed there
 * as mentioned above, features/libs are now enabled by default -> renamed FLOOR_CUDA_CL to FLOOR_NO_CUDA_CL and negate its use everywhere (+updated README accordingly)
 * fixed a case where "ifdef" FLOOR_NO_OPENAL should have been used
 * fixed the "ifdef" bool issue in vector_helper.hpp, this is now handled by essentials.hpp
 * fixed the const_string.hpp floor_fallthrough/[[clang::fallthrough]] issue, again, handled by essentials.hpp now
 * updated floor_prefix.pch a little
 * updated build_version.sh to also ignore floor_conf.hpp (would run into issues where the build version would get incremented if the enable/disable flags where changed otherwise, which should obviously not happen)