Move terraform options into new terraform types

[kaufers]

Creates a types.go that handles the definition of the terraform Options and the associated functions.

[GordonTheTurtle]

Please sign your commits following these rules: https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work The easiest way to do this is to amend the last commit:

$ git clone -b "tf-plugin-options" git@github.com:kaufers/infrakit.git somewhere
$ cd somewhere
$ git rebase -i HEAD~842354333104
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.

[codecov[bot]]

Codecov Report

Merging #833 into master will increase coverage by 0.01%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #833      +/-   ##
==========================================
+ Coverage   48.23%   48.24%   +0.01%     
==========================================
  Files          89       89              
  Lines        7974     7980       +6     
==========================================
+ Hits         3846     3850       +4     
- Misses       3771     3773       +2     
  Partials      357      357

Impacted Files	Coverage Δ
pkg/provider/terraform/instance/plugin.go	87.13% <100%> (+0.07%)	:arrow_up:
pkg/provider/terraform/instance/apply.go	69.1% <0%> (-0.64%)	:arrow_down:

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