Coding style normalisation

[DrizzlyOwl]

Why do we need this?
Dalmatian Tools has a lot of different contributors and there is no strict "house-style" for shell scripting. As a result we end up duplicating a lot of code or writing it in slightly different ways. This PR aims to address inconsistencies by adding a formatter called shfmt.

Notable changes include:

• Indentation style of 2 spaces
• Standard LF at the end of each line
• Final newline for each file
• Trailing whitespace must be trimmed

Quality of life changes include:

• Add more space around conditional statements and context differences to aid readability
• Referenced variables should be wrapped in {}
• Tests should use double [[]] instead of []
• if,for and while have ; then on the same line