Add remove-all-braces option

[mcsitter]

The option removes all braces inside the value field, if they don't contain a dollar sign.
If there is a specific case which would require a more complex regex, i am happy to make changes. I don't know how frequent dollar signs are for bibtex fields and what the entry would and after tidying should look like.

Maybe @tobirolinew can provide more info.

Closes #33

[FlamingTempura]

We should make sure that latex commands and escaped characters aren't broken by this option. These can appear outside of dollar signs, e.g.:

\`{A}
\textsterling{}
{\\fontencoding{LECO}\\selectfont\\char185}

How about only removing braces if there's not a slash command before or inside?

For quoted values we also have the case of the escaped quote "foo {"} bar". This syntax currently breaks bibtex tidy but I'm working on fixing it.

[FlamingTempura]

Superseded by cb45f7a