Add Jacobi preconditioner for mechanics

[dschwen]

Closes #69

[moosebuild]

Job Documentation, step Sync to remote on fc1e5fb wanted to post the following:

View the site here

This comment will be updated on new commits.

[moosebuild]

Job Coverage, step Generate coverage on fc1e5fb wanted to post the following:

Coverage

	74605a	#73 fc1e5f
	Total	Total	+/-	New
Rate	73.11%	72.60%	-0.51%	56.14%
Hits	3863	3887	+24	64
Misses	1421	1467	+46	50

Diff coverage report

Full coverage report

Warnings

• New new line coverage rate 56.14% is less than the suggested 90.0%

This comment will be updated on new commits.

[moosebuild]

Job Precheck, step Clang format on 84d1c24 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/73/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 23f6fecda543277adf4ff160631c1dfc28d790b1