Add support for date interval

[cgendreau]

ISO 8601 Date Interval : 2007-03-01/2008-05-11

[cgendreau]

Try to support other format like : 10.ix.1999 - 12.ix.1999 How can we check if a given string is a date range? Dates can contain numbers, roman numerals and month names in all different order. Some options: -Standardized date separators (e.g. only support slash as date separator) -Separator count, try to 'discover' the date separator by counting the different separators in the string -Regex, but it would be hard to catch all possible ways to write a single date @dshorthouse ?

[cgendreau]

Suggested initial support: 2 complete dates with a separator

• 9.v.1994 - 3.vi.1994
• 1977-08-16/1977-08-20
• 1910 Jul 23/1910 Jul 24

Not supported: partial dates or full start date and partial end date

• 1910 Jul 23, Sep 22
• 1917 Jul-Aug
• 1942 May 14-15

Those dates would require more processing and would bring new issues like 1910 Dec 23, Jan 5

[cgendreau]

Initial support available since 1.4