Fomating

Change keys\<account>.key structure to accounts\<account>\key.dat
Add unhex function and move tohex function to the new module hexparse.py
other formatting and minor change
Friendlist

add contact to friend list
load/save friend list as a file
post/fetch encrypted friend list

REMINDER: look up how MySQL checks whether a entry exits
Merge pull request #3 from vinocos/master

Friend list and formatting