Utility libraries

[coder137]

• Better optional support (std::optional has limitations)
  • https://github.com/TartanLlama/optional
• Add expected support (Return expected from a function instead of throwing exceptions)
  • https://github.com/TartanLlama/expected
• Guidelines Library
  • https://github.com/microsoft/GSL

[coder137]

#221 [Utility] Added tl::optional library and changed std::optional to env::optional (tl::optional underneath)