Some minor improvements to SMF\Time

[Sesquipedalian]

1. Workaround for a PHP date parsing oddity in SMF\Time::__construct()

   • In some versions of PHP, unexpected results may be produced if the $datetime parameter contains the special now or ago keywords and also contains a time zone ID string (e.g. now Europe/Paris), but that time zone ID string is different than the one in the $timezone parameter. 66b5a3a deals with that.

2. Improves input sanitization in SMF\Time::__construct()

   • This makes SMF\Time more robust than \DateTime in terms of the input it can accept. For example, the phrase "today at 5:30 pm" will actually work for constructing an SMF\Time object, whereas \DateTime would choke on the word "at" and fail.

3. Adds support for 'tomorrow' as a relative date format

   • This is helpful when showing upcoming events.

4. Moves Calendar::convertDateToEnglish() to Time::convertToEnglish()

   • It makes more sense as part of SMF\Time.

5. Tidies away some backward compatibility methods in SMF\Time

   • Just some housekeeping.