Add support for datetime annotation types

[Nicklas Nordborg]

This is a rather big change and will have effect in other parts of BASE as well. Here is a list of things that we need to do.

1. Add a new table for storing datetime values and a subclass to ParameterValues to handle it.
2. Add a new option to the Type enumeration.
3. Update the gui so that it is possible to add datetime values
4. Update the query api so that it is possible to search for datetime values
5. There are probably some effects also on the plug-in api since the Type enumeration and ParameterValues class are used by plug-in parameters as well. I'll have to investigate the effect and maybe add a specific ticket for adding datetime support to the plug-in system if the work required is substantial.
6. There may be similar effects on "extendable" classes (eg. reporters, users and raw data).
7. Check and update documentation
8. More...?

[Nicklas Nordborg]

Hmm... it seems like the table used to store dates is actually using a 'timestamp' column so theoretically it should be possible to use the existing table to store datetime values. And some (but not all) parts of the core api already allows the time part to be stored for date values. The main exception is that all string conversions to/from dates don't handle time and most of the gui is about string handling. I am trying to figure out what is the best:

• Use the existing table for both date and datetime values.
• Create a new table for datetime values and convert the old to only store date values

The latter is "cleaner" and is more correct according to the current documentation. The ability to store the 'time' part can be considered a bug. On the other hand, converting the existing table is an incompatible change which will cause data loss if someone is storing datetimes in it. It's not that likely though, since it can't happen with the official BASE release.

[Nicklas Nordborg]

Oh no... what a mess... I have to correct myself on the previous comment. It is possible to store datetime values with the current BASE release and it is not very complicated.

By changing the BASE->Preferences->Date format setting to a template that includes time placeholders (for example yyyy-MM-dd hh:mm:ss) it is possible to enter datetime values and the time part will be parsed and stored in the database. It messes up the query api though, since it will not match anything if not the exact date+time (including seconds) is entered as a search condition. Other users that hasn't changed the 'Date format' option will not be able to find any datetime values at all (except 00:00:00) since the time part is discarded before the query is made.

I think the "mess" needs to be cleaned up and they best way to do that is to make sure that no time part is getting into date-only values. Eg. we need one table for storing date-only values and one table for storing datetime values.