documentation: move readme to markdown and make it the doxygen mainpage

Author: rellla

Doxyfile

@@ -655,7 +655,7 @@ WARN_LOGFILE           =
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = .
+INPUT                  = .cpp .h README.md
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is
@@ -1790,3 +1790,5 @@ GENERATE_LEGEND        = YES
 # the various graphs.
 
 DOT_CLEANUP            = YES
+
+USE_MDFILE_AS_MAINPAGE = README.md