* doc: added base manual document

doc/manual/manual.doc

+/**
+
+\defgroup cpu Architecture Support
+
+\defgroup arm_common ARMv7
+\ingroup cpu
+
+\defgroup system Base System
+\brief The base system includes all extra functionality not necessarily ported to all supported platforms.
+
+\defgroup lib Library Code
+
+\defgroup net Network Stack
+
+\mainpage
+Welcome to the µkleos documentation.<p>
+
+*/