Add pin name comments in pal_default_config.

Added inline comments for all pin names in the pal_default_config
definition so it is easier to find the right element among all 32
elements in the array initializer.
Fix FRDM-KL25Z SWD_CLK/SWD_DIO/RESET pin defaults.

By default they were set as GPIO inputs, so the debug adapter could not
communicate with the KL25 MCU once the program started and changed the
SWD and RESET_b pins to GPIO configuration.

FRDM-KL25Z Reset/SWD pin assignments:

===== =========
Pin   Function
===== =========
PTA0  SWD_CLK
PTA3  SWD_DIO
PTA20 RESET#
===== =========
Improve default pin settings for FRDM-KL25Z.

Pins that don't exist on the MCU are set to UNCONNECTED.
Pins that are not dedicated to a particular use are set to INPUT_ANALOG
(we don't want them to be Hi-Z inputs if they are unconnected).
Pins that have special purposes such as RESET_b and SWD pins are set to
their special functions.
Fix blue LED (PTD1) assignment: set as output.
Merge pull request #1 from cdbennett/FREEDOM-KL25Z_Board_pin_init

Improve FREEDOM-KL25Z board pin initialization