[STM32xxx] CoIDE exporter and gcc_arm ...

- CoIDE options: wrap main and linker option DiscradUnusedSection=1 was
missing in some targets
- CoIDE options: corrected flash loader config for Nucleo_F030 and
Nucleo_F072
- CoIDE options: corrected memory layout (not used per default but now
it is the same as in linker script)
- gcc linker script: changed the memory size from hex number e.g. 0x2000
to decimal 8K

[DISCO_F429ZI] new target with [EXPORT] to gcc_arm and CoIDE ...

- build and export to toolchains gcc_arm and CoIDE is OK
- compiling is OK
- mbed/blinky is OK