Polish whitespace

Run "Reformat code" and "Optimize Imports" from within IDEA, cleaning up
trailing whitespace and other issues.
Favor use of Properties vs. for configuration

This reverts a number of changes made in commit 3033a19. Primary changes
include:

 - Restoring the immutability of the Node class

 - The argparse4j Namespace object is no longer passed down through
   Guice modules

 - Instead, arguments are eagerly read from the Namespace object by the
   #main method and these values are used to populate the Properties
   object that is already supplied to each Guice module

Other changes include:

 - The addition of a BootstrapNodes#DEFAULT_BOOTSTRAP_NODE field as
   a convenient alias to BootstrapNodes#DIGITAL_OCEAN_1 (or whatever the
   future default bootstrap node may be)

 - A Node#getPortAsString method has been added for convenience when
   dealing with String-based properties

 - A variant of the Node#at static factory method has been added which
   accepts the port value as a String vs. an int--again this is for
   convenience when dealing with String-based properties

 - Tests have been added to NodeTests to reflect the above