Normalize the language specification whitespace

[eernstg]

This PR makes no semantic changes to the language specification, but it changes many details about the whitespace and a couple of other formatting properties.

\commentary{} and \rationale{} blocks are indented consistently (that is, they indent the body by 2 spaces, which was previously only the case in some locations).

An empty line occurs before \begin{itemize} and before \begin{enumerate}, consistently.

In parenthesized commentary, the parentheses are consistently shown in commentary font (dimmed). This means that (\commentary{...}) was changed to \commentary{(...)} in a number of locations.

Added/removed a missing/extra space (...}or ... --> ...} or ... and which is --> which is, some double spaces after a period or colon).

A non-trivial number of locations may seem to have been modified because a line break was moved (typically because some lines were too long after indentation).

[eernstg]

Note that reviewing can be done with a "Hide whitespace" setting which will reduce the number of lines in the diff very substantially.