GEOMESA-265, 264, 263 Create a tools wrapper shell script, Make output for `list` command line tool prettier, and StatsWriter Exception when exporting

    This adds a wrapper shell script to the existing geomesa-tools and changes up a lot
of the way things used to work on geomesa-tools. First, --help is completely changed and
works on individual commands, rather than just dumping the whole usage text. `describe` is a
new feature that describes the attributes on individual features. `list` now only lists
the names of features on a catalog table. Almost every flag has a single character
option. Accumulo username and password can be specified with -u/--username and -p/--password
on the command line. One can also only give a username and geomesa-tools will give an additional
prompt for password, therefore not putting it in the shell history. A geomesa-test-script.sh is included
under /bin to run every command in a chain, just to ensure things are working on your individual machine.
You will have to customize this script with the correct username, password, catalog table, feature name, and spec. The
README has been greatly updated to reflect the changes made through this PR. Finally, many stylistic changes
were made from a meeting with the Geomesa Dev team on this past Friday, with more plans to add to geomesa-tools.