Modify doxygen layout for g documentation
Modify doxygen layout for g documentation

Include link to EGSnrc documentation page in the standard doxygen
layout, generated using `doxygen -l`.

mchamberland/EGSnrc,mchamberland/EGSnrc,crcrewso/EGSnrc,crcrewso/EGSnrc,crcrewso/EGSnrc,mchamberland/EGSnrc,crcrewso/EGSnrc,nrc-cnrc/EGSnrc,nrc-cnrc/EGSnrc,nrc-cnrc/EGSnrc,nrc-cnrc/EGSnrc,mchamberland/EGSnrc,nrc-cnrc/EGSnrc,MartinMartinov/EGSnrc,crcrewso/EGSnrc,mchamberland/EGSnrc,MartinMartinov/EGSnrc,MartinMartinov/EGSnrc,MartinMartinov/EGSnrc,MartinMartinov/EGSnrc,mchamberland/EGSnrc