stm32l1: initial port for the nucleo-l1 board and stm32l1 cpu

boards/nucleo-l1/Makefile

boards/nucleo-l1/Makefile.features

boards/nucleo-l1/Makefile.include

boards/nucleo-l1/board.c

boards/nucleo-l1/dist/debug-server.sh

boards/nucleo-l1/dist/debug.sh

boards/nucleo-l1/dist/flash.sh

boards/nucleo-l1/dist/gdb.conf

boards/nucleo-l1/dist/openocd.cfg

boards/nucleo-l1/dist/reset.sh

boards/nucleo-l1/include/board.h

boards/nucleo-l1/include/periph_conf.h

cpu/stm32l1/Makefile

cpu/stm32l1/Makefile.include

cpu/stm32l1/cpu.c

cpu/stm32l1/hwtimer_arch.c

cpu/stm32l1/include/cpu-conf.h

cpu/stm32l1/include/hwtimer_cpu.h

cpu/stm32l1/include/stm32l1xx.h

cpu/stm32l1/lpm_arch.c