time span format verbosity

[neilboyd]

Fixes #571
Fixes #642
Fixes #969

Based on HeadingStyle (although that's inconsistent with WordForm).

Replace timeSpan.Humanize(toWords: true) with timeSpan.Humanize(timeSpanStyle: TimeSpanStyle.Words).
This is a breaking change.

timeSpan.Humanize() remains unchanged, although the optional parameter has changed from toWords: false to timeSpanStyle: TimeSpanStyle.Full.

Added timeSpan.Humanize(timeSpanStyle: TimeSpanStyle.Abbreviated) and timeSpan.Humanize(timeSpanStyle: TimeSpanStyle.Short).
These return English regardless of the locale.

Question: how do you normally handle translation in this project? I could add tests for every language, where Abbreviated and Short return English for every locale, or not, or I could create translations (and tests) for every language (I could make a best guess for Latin and Cyrillic alphabets, but not the others).

Question: should we use uppercase for Y, D, W? (M is already uppercase in order to disambiguate with minute)

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[neilboyd]

I think it's ready, but there are some questions in the description

[SimonCropp]

@hazzik thoughts on this one?

one note is that it significantly increase the number of entries in all the resource files. but if the entry is missing it can sensibly fall back to an acceptable value

[hazzik]

I'm refactoring this whole thing into using fewer resources:

DateHumanize_MultipleDaysFromNow ("{0} days from now") would become:

DateHumanize_Future => "{0} from now" (new resource) and
TimeSpanHumanize_MultipleDays => "{0} days" (existing resource)

After that refactoring we could start thinking about abbreviations.

[SimonCropp]

@hazzik awesome. love your work

[hazzik]

I've tried to refactor *Ago and *FromNow. Unfortunately it is not an easy task :( Too many language specific rules.