Prefire 2.0

[BarredEwe]

A branch containing all the big changes.
Feel free to include more elements to the list if I've missed anything:

Main

• Add support for working with #Preview Macro.
• Create an .executableTarget to be able to run through the terminal.
• Add correct error output from snapshots.
• Add the perceptualPrecision parameter setting.
• Add a check for the current color theme. (Not in this release)
• Pass the imports to the PreviewModel.

Tests

• Run tests using CI
• Tests for getting config file.
• Tests for parsing config file.

Documentation

• Describe all changes in the documentation