Write new expression parser from scratch to support conditionals

[dschwen]

Closes #100

[moosebuild]

Job Documentation, step Sync to remote on 0ab01d2 wanted to post the following:

View the site here

This comment will be updated on new commits.

[moosebuild]

Job Coverage, step Generate coverage on 0ab01d2 wanted to post the following:

Coverage

	636686	#101 0ab01d
	Total	Total	+/-	New
Rate	73.69%	76.66%	+2.96%	100.00%
Hits	4034	4397	+363	864
Misses	1440	1339	-101	0

Diff coverage report

Full coverage report

This comment will be updated on new commits.

[moosebuild]

Job Precheck, step Clang format on 0bed4eb wanted to post the following:

Your code requires style changes.

A patch was auto generated and copied here
You can directly apply the patch by running, in the top level of your repository:

curl -s https://mooseframework.inl.gov/swift/docs/PRs/101/clang_format/style.patch | git apply -v

Alternatively, with your repository up to date and in the top level of your repository:

git clang-format 63668614e1c87e678d5fbf6ccfe886a1742ab95e