I2C needs to be reworked to use IT mode

The I2C layer needs some patches (twi.c in core):

• IRQHandler name do not match for F0 & L0
• ER_IRQn needs to be attached for all boards (except F0 & L0)
• Errors need to be taken account in master_read & master_write
• Error Callback must be reviewed to work in slave & master mode
• Other (to see)?

[fpistm]

Buffer size could be reviewed to avoid #120. Handled by #124

[fpistm]

FYI: I've revert the commit which introduce I2C IT:
625fe2d

Let's reintroduced this thanks this issue solving.