Internationalized date/time formats

Glom now interprets and displays dates and times according to the formats used in the user's locale. In C++ that requires the use of the time_put<&qt; and time_get<&qt; facets, which are not very pretty. Daniel Elstner did a great code-review of my locale stuff, so I learnt lots along the way. There is one small glitch – as far as I can tell, time_get<&qt; in gcc can not parse the time for any locale other than C. Here is a little time_get<&qt; test case if anybody would like to show me my error.

Soon I need to start a custom TreeModel so that the Data List view can show large amounts of rows from the database without copying insane amounts of data.