tcl STM32L0xx - add support for dual banked targets and for Nucleo-64 STM32L073

tcl STM32L0xx - add support for dual banked targets and for Nucleo-64 STM32L073

- stm32l0_dual_bank.cfg - implement dual bank configuration

- st_nucleo_l073rz.cfg - implement new board script

Change-Id: Ie8063e5bec45069a63d414d81b2068fe3cc7e4d7
Signed-off-by: Jan Čapek <jan.capek@braiins.cz>
Reviewed-on: http://openocd.zylin.com/3957
Reviewed-by: Cezary Gapiński <cezary.gapinski@gmail.com>
Reviewed-by: Karl Palsson <karlp@tweak.net.au>
Tested-by: jenkins
Reviewed-by: Aurelio Lucchesi <me@0rel.com>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>