Nested braces

Adds:

* Test for bash-like `**` (in addition to current style)
* Test for nested brace expansion
* Test for `{1..100}`-style numeric expansion
* Test for `:` for property assignment (in addition to `=`)
* Test for repeated section names (eliminates implementations using hash maps for sections)
* Add test for case insensitivity for `true` in `root = true`
* Change tests for `[/]`

Should `root` be case insensitive also?  Does it matter?