STM32 L0 memorymap and GPIO module

This Pull Request adds new suport for STM32 L0 family. Currently only GPIO peripheral is validated with datasheet. Others will follow.


this file is almost same as the one (from l1? ... forgotten from where I was copied it) but with different base address of BRR register. Should be checked if it is bug in the other file, or ST has more versions of GPIO peripheral.