This is a huge patch and adds formatting of indentation. It is slightly
difficult to come up with a good set of rules but I think what is here
is pretty nice. There are two types of indentation: block/hard
indentation and continuation/soft indentation.
Block indentation are context independent and are thus "hard" or
required in the sense that they always happen. Block indentation are
enabled for all `x - end` blocks where `x` is one of `begin`, `do`,
`for`, `function`, `if`, `let`, `quote`, `struct`, `try`, `while`. A
notable exception is `module`, but one idea is to indent nested modules
(in the same file).
Continuation or soft indents are context dependent in the sense that if
nested within another soft indent they extra indents are skipped. Soft
indentation applies to all expressions spanning multiple lines.
For example, newlines in operator chains:
```julia
a + b * c +
d # soft indent
```
function calls
```julia
foo(
a, b c, d # soft indent
)
```
etc.