net: added RD client for simplified registration

Makefile.dep

makefiles/pseudomodules.inc.mk

sys/Makefile

sys/auto_init/auto_init.c

sys/include/net/rdcli_common.h

sys/include/net/rdcli_config.h

sys/include/net/rdcli_simple.h

sys/net/application_layer/rdcli_common/rdcli_common.c

sys/net/application_layer/rdcli_simple/Makefile

sys/net/application_layer/rdcli_simple/rdcli_simple.c

.../application_layer/rdcli_simple/rdcli_simple_standalone.c