IO Parameters - FieldOutput (1/X)

[landinjm]

• Please check if the PR fulfills these requirements

• The PR follows our guidelines (formatting & style)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Created a new IO parameters file where all IO parameters will live. Currently, only the field output parameters have been written.

• What is the current behavior? (You can also link to an open issue here)
  Currently, parameters are declared in InputFileReader, read inUserInputParameters, and packaged into their respective parameter subclasses. This is a bad way to do it because you have to edit and understand several files in order to add parameters. This makes is burdensome and more difficult to unit test individual parameter files. They are also interlinked, which adds to the issue.

• What is the new behavior (if this is a feature change)?
  Now, each parameter class does five things.

1. Declare parameters
2. Read parameters
3. Postprocess parameters
4. Validate parameters
5. Package parameters into a minimal struct

This allows us to do the following things more easily

• Write unit tests
• Add new parameters
• Let users avoid using parameters.prm entirely

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No. These parameters are not used currently.

• Other information:
  Works on Add user input for the output compression level #671, Add a flag to choose what fields are saved to vtu #502, Add option to suppress output for specific fields #721, UserInputParameters should not be templated based on dimension #704, Let user specifiy output directory #673, Add unified parameter class interface #606, the user_inputs folder is a mess #572, Add in manual that the output file name can be used to change the output directory #147, write unit tests for the parameter validation functions #573, N_PER_DECADE Doxygen documentation unclear #259