Reformat documentation to use triple-slash doxygen format.

[Dimi1010]

Rationale:

• Reduced line bloat. Each documentation block is 2 lines shorter on average.
  This can compound to over 100 lines on some of the larger files. (e.g. "IPAddress.h")
• Makes usages of comment blocks /* */ easier to manage during refactoring, as they won't be terminated early if there are documentation comments inside them.

Progress summary:

• Common++
  • Namespace and file docs (Reformat Common++ documentation to use triple slash. #1647)
  • Class and Struct docs (Reformat Common++ documentation to use triple slash. #1647)
  • Enums (unsure if these are property formatted already)
• Packet++
  • Namespace and file docs (Reformat Packet++ documentation to use triple-slash doxygen format. #1659)
  • Class and Struct docs (Reformat Packet++ documentation to use triple-slash doxygen format. #1659)
  • Enums
• Pcap++
  • Namespace and file docs (Reformat Pcap++ documentation to use triple-slash doxygen format. #1660)
  • Class and Struct docs (Reformat Pcap++ documentation to use triple-slash doxygen format. #1660)
  • Enums