Migrate HTTP sessions

Note: In Version 5 and higher, default write frequency mode is TIME_BASED_WRITES, which is different from Version 4.0.x default mode of END_OF_SERVICE.

Migrating from Version 4
No programmatic changes are required to migrate from Version 4 to Version 6.0.

Migrating from Version 5.x
No programmatic changes are required to migrate from Version 5.x to Version 6.0.