Support using %seed with local file path

[michaelnchin]

Issue #, if available: #44

Description of changes:

• Added new options to %seed to support loading from a specified file location.
  • --language: Specifies which language endpoint(gremlin,cypher, or sparql) to submit the queries to.
  • --source: Specifies the full path to a data file, or a directory containing multiple files, that you would like to load queries from.
  • -f/--full-file-query: If using Gremlin or openCypher, specifying this flag will submit the entire content of the file as a single query, instead of one query per line.
• Removed sample seed data from package. Samples will now be loaded from an external S3 bucket.

Example run with arguments to load from a local file:

%seed --language Gremlin --source /Users/foo/seed_directory/data_file_0.txt -f --run

Running %seed by itself will allow you to select the same options.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.