Fix #206

not working, disabling until we found the issue.

Otherwise a compulsory property should be added to every board (3rd paty hell).
The bug is related with IDE's uploadUsingPreferences; the property map used to expand the receipe is derived from board properties and overwritten by the programmer's properties.
So no default can exist, and no global variable either.

Main differences:

* avrdude compatible vs bossac bootloader
* flash location of user sketch (0x2000 vs 0x4000)

Add method to automatically retrieve sketch start

Use the information retrieved from the linker script in use to simply call a reset without any erase

The exported variable is used by banzai() to avoid erasing any bootloader part

Change alignment in linker script, to remove build warning with I2S lib

Changed 'containts' to 'contains' and 'Continuos' to 'Continuous'.