Improve serialization and deserialization of enumerables of primitive types

[mkommend]

The DataImporter uses List<double?>, List<DateTime?> and List<string> quite heavily. These types are currently serialized using the default EnumerableSerializer and thus every element is processed separately. To improve the persistence speed a specialized EnumerableSerializer should be implemented, which can handle the specified types.

[gkronber]

This is mainly relevant for the DataImporter which should be integrated into the trunk soon.

[epitzer]

r10896 make the Number2StringSerializer accept nullable numbers

[abeham]

There has already been a commit in the trunk a while ago. Please make sure this ticket is released rather sooner than later.

[epitzer]

r11352 add more test cases to ensure proper serialization of nullable types

[epitzer]

This concludes the first part of the request (compact serialization of nullable types). Adding compact serialization of string enumerables requires more work to ensure correct handling of escapes, unicode and embedded CDATA sections. If this feature is still required I propose to put it into a new ticket.

[mkommend]

Reviewed r10896 and r11352.

[mkommend]

r11373: Merged r10896 and r11352 to stable.