Removed update calls from EnvironmentVariableResource.destroy,
ApplicationResource.addEnvironmentVariable,ApplicationResource.addEnvironmentVariables,and
ApplicationResource.removeEnvironmentVariable. 
Resolves #1, Resolves #2

Added
ApplicationResource.removeEnvironmentVariable(IEnvironmentVariable)
Resolves #9

Renamed environmentVariableByName to environmentVariableMap

Updated getOrLoadEnvironmentVariable to work check for emptiness of
environmentVariableMap

Updated loadEnvironmentVariables to work on environmentVariablesMap, and
return it, in contrast to a locally-scoped version that did not persist.
Corrected test failures due to omitted changes to instances methods.

Resolves #3, Resolves #6