Swap datetime.date for datetime.datetime (sub-day and add timezone support)

[amalizzio]

Discussed in https://github.com/disentcorp/dateroll/discussions/15

Is your feature request related to a problem? Please describe. Would like

• be drop-in replacement for datetime.datetime
• support for $<$1d time periods
• support for multiple timezones
• update parser to work for TimeStrings (to be spec'd)

Describe the solution you'd like

• Use datetime.datetime as base class for dateroll.Date
• Support for time-slicing and range-indexing on whole periods (i.e. datetime.datetime(2024,None,None) ... for whole years, quarters, months, weeks, (days is native), hours, minutes. (will need detailed specifications). Always for multiple bucketing approaches for rollups (akin to excel pivot table row groupings and panders grouper)

Describe alternatives you've considered Review https://github.com/wroberts/pytimeparse against parser for TimeStrings.

Additional context tbd

[Batu4]

Summary:

• created a new branch: feat-subday-timezone
• new settings for timezone (default=utc)
• added hours,minutes,seconds into Duration Class functions
• replaced datetime.date into datetime.datetime but the dates of holidays are datetime.date

TODO:

• make datetime.datetime work for ddh,parser and parsers classes
• update parser to work for Timestrings would like to ask about multiple bucketing approaches

[Batu4]

Summary:

• added timezone with default timezone as local computer timezone
• intraday time works on all classes eg ddh(string), Date(y,m,d,h,min,s,us)
• string of hour, minute, second, microsecond are h,min,s,us
• adding subtracting on date with intraday works now
• all tests passed and coverage is 100%
• cleaned the code