WIP: Advanced line wrapping

• Adds a wrap style option to themes which allow user to choose between wrapping greedily or splitting the lines evenly.
• Adds a optional line wrap "[ ]"
• Wraps lines evenly prioritising "[ ]" then "," then " ".

fixes #300, #871

TODO:

• Implement optional line wrap
• Implement even line wrapping
• Add setting to change line wrap strategy [Fill line, Even]
• Decide on default line wrap strategy (I'd love to default to even, but to keep consistent with previous versions and to keep the code base clean, I'm defaulting to greedy)
• Choose an optional line wrap character sequence most people are happy with (sticking with "[ ]")
• Write some tests
• Submit code for #871 (Not required but recommended)
• Test RTL languages
• Allow editing line wrap character order of preference