Update debug to note I2CS devices as potential sources of error

An I2CS device will respond with a NACK if you try and control it with the PLM
before it is linked as a responder.  Add a note to the debug log regarding this.
Fix typos in AllLinkDatabase

ALDB was accidently typed ADLB in a few places.  These are likely causing some unnoticed errors, particularly with sorting.
get_first_empty_address should return 0 if no addr

The sub add_link expects get_first_empty_address to return 0 if no empty address is found.

This will prevent trying to add an aldb record to the FFFFFFFFFFFFFFF8 address which clearly doesn't exist.  Instead the user will now get a nice error advising them to scan the link table before trying to sync links.

It appears that something about Marc Merlin or my changes have some difference in the line endings.  Not sure why the additional lines are listed as changed.
Merge pull request #41 from krkeegan/aldb_typos

Fix typos in AllLinkDatabase
Merge pull request #40 from krkeegan/empty_aldb

get_first_empty_address should return 0 if no addr
Merge pull request #39 from krkeegan/nack_error_i2cs

Update debug to note I2CS devices as potential sources of error
Revise NACK error Message for I2CS Devices

Add suggested language requested by Marc.
Merge pull request #42 from krkeegan/nack_error_i2cs

Revise NACK error Message for I2CS Devices