BENTO-15 (Part 3). Adds UUID generation tool and script.

This commit adds a tool and run script that generates a UUID and writes it
to a file in the user's home directory. Various maven pom changes are made
and build resources added to support developing java code in kiji bento. The
release assembly is modified so that the script is properly packaged as part
of bento-cluster in the bento box.
BENTO-15 (Part 4). Implement usage timestamp recording.

This commit adds a new tool that will record the current time in
milliseconds in a file .kiji-last-used in the user's home directory.
This tool is used by the kiji script in a BentoBox to record the last
time a user used the `kiji` command.
BENTO-15 (Part 5). Kiji BentoBox can be queried for its version.

This commit adds a class, VersionInfo.java, which can be queried for the current
version of Kiji BentoBox. A properties file that helps in this functionality is
also added a resource to the project.
BENTO-15 (Part 6). Add UpgradeResponse to kiji-bento.

This commit adds a class UpgradeResponse to kiji-bento. This class represents
upgrade information returned by the BentoBox upgrade server, and also allows
for tracking the time the user was reminded of the upgrade.
BENTO-15 (Part 7). BentoBox can inform the user of upgrades.

This commit adds a tool to BentoBox, UpgradeInformerTool, that will display
upgrade information if such information is saved in a file at
cluster/state/.kiji-bento-upgrade in the user's BentoBox distribution.
BENTO-15 (Part 8). Add check-in message to Kiji BentoBox.

This commit adds a class, UpgradeCheckin, to BentoBox. This class will be used
to construct check-in messages to be sent to the Kiji BentoBox upgrade server.
BENTO 15 (Part 9). Client for the BentoBox upgrade server.

This commit adds a class which acts as a client to the BentoBox upgrade
server. This class can be used to send check-in messages to the server and
receive response.
BENTO-15 (Part 10). Thread that periodically checks-in with upgrade server.

This commit adds a thread that will periodically send a check-in message
to the upgrade server, receive a response, and write the JSON in the
response to a file on the local filesystem.
BENTO-15 (Part 11). Tool for running check-in thread.

This commit adds a tool which launches a check-in thread and waits for
its completion. The tool installs a shutdown hook and writes a PID file
so an external process can shutdown the daemon.
BENTO-15 (Part 12). Scripts to start and stop upgrade daemon.

This commit adds the start and stop scripts for the upgrade daemon.
It also updates the README with information on upgrade checkins.
Code review changes.