Set optimization level to 0, Set printf() support to minimal - no special floating point and special format symbols except for c,o,d,x,s,%

The previous value of 512 B is often insufficient when using
the printf family of functions.

New objective:
 - Toggle D1 with 2 Hz
 - Turn off D2 if USR_SW1 is pressed
 
Also, refine comments and explain the timing better.

GPIOPadConfigGet() requires pin number as second parameter instead of
bit packed representation

Reordered GPIOPadConfig*() and GPIOPinTypeOutput() to let GPIOPadConfig*
() take effect