Fix bugs parsing Chameleon TALES expressions

[dokai]

Previously lingua had problems parsing TALES expressions which contained either a

• tal:repeat with a parenthesized expression as the first part
• prefix (e.g. python:, string:, etc)
• structure keyword (BBB)
• multiple expressions separated by a pipe

[wichert]

For some reason I missed this pull request, and in the meantime I've made a few changes which conflict with this :(

Can you update your pull request to fix the conflicts?

[wichert]

This is now fully covered by #32, #35, #36 and #37, thanks to @iksteen.