Add "all days" to the Dates: menu to search entire audit logs

[rklrkl]

It doesn't appear that it's easy to search your entire audit history. The only way seems to be to use the "Custom date range..." option in the Dates: menu and then try and pick a start date older than (or the same as) when you first ever installed the plugin....which could be hard to remember if it's months or years ago, Yes, you could put "1970" as the year, but that just shows how clumsy the whole process is.

It would be much easier if the Date: menu had an option for the entire logging period (e.g. "All days" or something like that). I can't see why that's not in there, especially when you already paginate the search results.

[rklrkl]

It should be noted that this only needs to be implemented if issue bonny/Simple-History-Plus#4 is also implemented, since the current max retention time for audit logs is a surprisingly low 60 days.