Add ElsePlacement linter

Add linter which enforces the placement of `@else` directives.

Users can choose to prefer `same_line` or `new_line` to indicate they
prefer

    } @else {

or

    }
    @else {

...respectively.

`@else` directives on the same line as the preceding `@if` directive are
ignored.

Change-Id: I58880c1f78d466a5c6dcf20e5b31fdeaab098a14
Reviewed-on: http://gerrit.causes.com/38487
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Reword spec descriptions for HexLength examples

These were lacking the preferred "when" prefix.

Change-Id: Ia15dfb08d9ad2ba0ac8f427835421eca59b92eaf
Reviewed-on: http://gerrit.causes.com/38488
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>