Fixed bad method call

missing self.
Fixes to SNAP platform

Added sources attribute
Fixed FPGA model (no caps)
Added logging to yellow blocks
Added SNAP constraints top.v

currently both are just copies of the kc705
Addded missing adc16 source file names
Added adc0_clk as supported SNAP clk
Switched to vivado 2014.2
Catch error when topfile doesn't exist

Otherwise toolflow will carry on regardless and if an old
top.v is at the appropriate destination will merrily go ahead
and edit that one.
Change env variable to point to vivado 2014.2