[NUCLEO_F302R8] Add I2C slave, enhance I2C master
typo
K20D5(0)M SPI code

Other pinouts still need to be done. PTC6 as MOSI possibly has issues.
There are also some changes which technically aren't required, but were
made in the search to why on earth it wasn't doing anything.
Merge pull request #311 from Sissors/K20

[K20D5M] SPI implementation - freq
Merge pull request #312 from mazgch/master

fix wrong pin in C027 platform api
[NUCLEO_F030R8] enhance I2C master
[NUCLEO_F302R8] indentation correction in I2C api
Merge pull request #310 from dbestm/master

[NUCLEO_F302R8] Add I2C slave, enhance I2C master
Fix exporters on UBLOX_C027

Temporary solution, until the exporter infrastructure is modified
to support proper target aliasing/inference.
Update Exporter README
Add NRF51822 to exporter readme
[NUCLEO_F302R8] enhance SPI slave
Merge branch 'master' of https://github.com/mbedmicro/mbed
Merge pull request #313 from dbestm/master

 [NUCLEO_F302R8] enhance SPI slave
Bumped revision number
Added LPC11U68 to the official build