Doxygen warnings corrected

* Doxygen spits out a lot of warnings about not being able to find
  match function signatures, etc. This is because in some headers we
  have a using namespace statement, in others it gets confused between
  ::Window and Window (!).

* Wrong use of tags:
  + Lots of @seealso - should be @see
  + Wrong usage of @overload - corrected with the right function
    signature
  + HTML tags that doxygen doesn't recognize removed

Change-Id: I1c2eed941619b8764dbfcfc5ab38027518cdf261