Feature/inLineSource: adding another source type

[gnguyen87]

Description & motivation

From this Monday item:

Consider adding another source type, possibly called inline, where the data is specified in the earthmover YAML:

sources:
  inlineSource:
    orientation: rows # or columns
    data:
      - key1: value1a
        key2: value2a
        key3: value3a
      - key1: value1b
        key2: value2b
        key3: value3b
      - key1: value1c
        key2: value2c
        key3: value3c
    # or, if orientation=columns
    data:
      key1: [ "value1a", "value1b", "value1c" ]
      key2: [ "value2a", "value2b", "value2c" ]
      key3: [ "value3a", "value3b", "value3c" ]

This PR supports this feature by adding a new inLineSource class with minor refactoring to other helper classes.

PR Merge Priority:

• Low
• Medium
• High

Changes to existing files:

• source.py : Add an inLineSource class
• runs_file.py: Import inLineSource class to take care of file-hashing
• column.py: Cast dict vals to str type in a lambdato appropriately join row values together
• earthmover/tests: add an inLineSource to the test suite

Tests and QC done:

• Tested locally via the test suite as well as earthmover_edfi_bundles

[jayckaiser]

Consider InlineSource to fit convention of other nodes.