porting STM32L Discovery sources to open source tools.

Based on existing work from Eclipse Plugin GNU ARM Eclipse Plug-in - http://gnuarmeclipse.sourceforge.net/updates and STM32L-DISCOVERY package sources.

If you like to use JTAG via OpenOCD you need to download an build openocd yourself as version 0.7.0 has a problem in flash handling of stm32f15x chips.