server: fix shadowed port variable
server: add Basic HTTP Authentication for PUT requests
server: make #port: an instance method
server: #port now returns the correct port number
server: rename class side #port to #defaultPort

additionally initialize instances with defaultPort
server: handle server arguments in separate method
server: add separate setters for username/password
server: better parsing of commandline options
server: extract commandline actions into separate method
server: check for even number of arguments, otherwise use default values
server: only authenticate if username/pw were set
Merge pull request #288 from mkroehnert/auth

add 'Basic' HTTP Authentication to Amber server