Sanoid - Set specific times for snapshots

[redmop]

Weekly_day
Weekly_time
Daily_time
Monthly_day (allow last day of the month)
Monthly_time

If no snapshots of a specific time exist, still take immediately.
If snapshots are older than the time interval, take immediately, then again at the requested time

[redmop]

Weekly time includes min and hour. May need to break this up.

[redmop]

Handle not always on. AKA If snapshot daily is over 24 hours old, take immediately, and again at the requested time (even if less than 24 hours)

[redmop]

Ok, well, this is mostly done already.
We just need weeky_day, weekly_hour, weekly_min.

I'll drop end of month stuff because beginning is already there.

[redmop]

Weekly is in testing now.