Parse and store sortID

[cgars]

The abtract JSON model contains an sortID field. The abstracts should be shown sorted according to this number and the sortID therefore needs to be stored in the databse.

Furthermore sortID itself encodes two things. 1.) the group id of the poster 2.) The poster number. They are combined such that the leftmost 16 bit are an int_16 representing the poster group id and the rightmost 16 bit an int_16 representing the poster number.
groupID = int((sortID & (0xFFFF << 16)) >> 16)
poster_numer = int(sortID & 0xFFFF)

see also
https://github.com/G-Node/GCA-iOS/blob/master/GCA/Abstract%2BUtils.m

Both the group_id and the poster_number should be retrieved and stored. The Abtsract fulltext should show both groupname and poster number.