JuliaDT should default to the code formatting conventions recommended for Base Julia

[tkelman]

Ref https://github.com/JuliaLang/julia/blob/master/CONTRIBUTING.md#general-formatting-guidelines-for-julia-code-contributions, mostly indentation style is what the formatter here has control over. Auto-removal of trailing whitespace when the autoformatter is run would also be neat, but a nice-to-have rather than a hard requirement.