Add 'include_column_list' parameter

[eeshugerman]

I found this un-merged patch by @kyrozetera on the old databricks repo (link), and it solves an issue I'm facing.

My use case

Many of the Redshift tables that I'm working with have created_dt columns, like so:
created_dt timestamp not null default current_time
These columns are intended to be left unspecified on inserts/copies, so that the default is used. But for this to work, a column list must be included in the COPY statement, or else I get an error: Missing data for not-null field

Author's use case

It appears the author's motivation for this patch is related to, but different than my own: databricks#340

[codecov-io]

Codecov Report

Merging #58 into master will increase coverage by 0.16%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
+ Coverage   73.92%   74.09%   +0.16%     
==========================================
  Files          15       15              
  Lines         767      772       +5     
  Branches      103      106       +3     
==========================================
+ Hits          567      572       +5     
  Misses        200      200

[lucagiovagnoli]

This looks great! Thanks for the pull request. Can you please:

1. address comments
2. Bump version and changelog (patch version should be ok as this is backwards compatible)

[lucagiovagnoli]

why is the schema null here? (in the Map object MAP[Table, StructType]). Should we use the TestUtils.testSchema ?

[eeshugerman]

Not sure, but I'm guessing the original author copied it from the test above this one, which for some reason uses null. I've changed it to TestUtils.testSchema.

[lucagiovagnoli]

Could you please write a second small test near this one showing the difference when include_column_list = false ?

[eeshugerman]

Thanks for reviewing @lucagiovagnoli! I've made the requested changes to the tests.

2. Bump version and changelog (patch version should be ok as this is backwards compatible)

I bumped the minor version instead, since this PR adds functionality. From https://semver.org:

Given a version number MAJOR.MINOR.PATCH, increment the:
MAJOR version when you make incompatible API changes,
MINOR version when you add functionality in a backwards compatible manner, and
PATCH version when you make backwards compatible bug fixes.

But I can switch to patch if you prefer.

[lucagiovagnoli]

minor works! I was exactly trying to follow semver but got confused.