LTL to English improvements

[sidprasad]

English to LTL translations mechanical and potentially ambiguous. Add support for better translation.

[PatrickTrentin88]

An example:

It is always the case that 'n' holds is necessary for eventually, 'p' holds

The question wanted me to read it as

(it is always the case that 'n' holds) is necessary for (eventually, 'p' holds)

but I read it as

it is always the case that (('n' holds) is necessary for (eventually, 'p' holds))