SCHEMA-801. Correctly handle empty columns

issue: https://jira.kiji.org/browse/SCHEMA-801
review: https://review.kiji.org/r/1894
SCHEMA-803. Harden KijiSchema shell script.

 - Delete extraneous? conf/ directory
 - Improve developer kiji script.
 - Remove unused/unusable foreground option
 - Normalize conditionals:
   * use [[ ... ]] instead of [ ... ]
   * use && instead of -a and || instead of -o
 - Fixes indentation some.
 - Normalize variables from $x to ${x}
 - More documentation and fixes.
 - Explicitate that shell ${kiji_schema_version} is Maven ${project.version}
 - Document ${KIJI_HOME}/lib/distribution origin.

issue: https://jira.kiji.org/browse/SCHEMA-803
review: https://review.kiji.org/r/1899
SCHEMA-802. Log warning when uninstalling instances and deleting tables with registered users

issue: https://jira.kiji.org/browse/SCHEMA-802
review: https://review.kiji.org/r/1898
Fixes an issue with Maven replacing ${class} in scripts while assembling.
[maven-release-plugin] prepare release kiji-schema-root-1.4.2
[maven-release-plugin] prepare for next development iteration
SCHEMA-806. Revamp (fix and improve) kiji shell script.

 - Improve DEBUG mode (logs file:line)
 - Document environment variables.
 - Emit warnings when required environment variables are not set.
 - Add kiji env-check to dump and validate the environment.
 - Document priorities between environment and path.
 - Disable Maven assembly filtering of shell-scripts.
 - Beef-up profiling enable/disable scripts.

issue: https://jira.kiji.org/browse/SCHEMA-806
review: https://review.kiji.org/r/1903
SCHEMA-811. Improve KijiCell API

issue: https://jira.kiji.org/browse/SCHEMA-811
review: https://review.kiji.org/r/1910
SCHEMA-810. Hide KijiColumnName constructors behind a factory method

issue: https://jira.kiji.org/browse/SCHEMA-810
review: https://review.kiji.org/r/1909
SCHEMA-809. Migrate KijiResult from Iterator to KijiResultIterator

issue: https://jira.kiji.org/browse/SCHEMA-809
review: https://review.kiji.org/r/1907
SCHEMA-813. Split ZooKeeperFactory out of HBaseFactory, remove LocalLock, reference track Curator ZK connections

issue: https://jira.kiji.org/browse/SCHEMA-813
review: https://review.kiji.org/r/1911
SCHEMA-811. Improve KijiCell API

issue: https://jira.kiji.org/browse/SCHEMA-811
review: https://review.kiji.org/r/1918
SCHEMA-800. Create method for building a map from a KijiResult.

issue: https://jira.kiji.org/browse/SCHEMA-800
review: https://review.kiji.org/r/1917
SCHEMA-814. Implement Comparable for KijiRowKeyComponents.

issue: https://jira.kiji.org/browse/SCHEMA-814
review: https://review.kiji.org/r/1914