fsttable objects are grouped into a fststore

[MarcusKlik]

Some operations might require temporary files. For example, a large slice map or a newly created column can be stored in an additional fst file.

When these potentially large temp files are stored in a temp directory, that might cause a problem for the user. They might not be cleaned very often and large fst files will quickly fill up the users disk.

Perhaps it would be nicer to organize the fsttable's in a fststore (better name required :-)). The temp files can be kept organized and cleaned more easily