group.index // txt file poco propertie format 
 group hash = folder name (group_1 -> ...) uint32

group_folder
 // binary, konto hash = kto index uint32 (first in transaction, getting 1), sorted by hash
 // hash at end of file
 // sort in memory, file is unordered, maybe for small files linear search is faster
 // put last used in cache
 pubkeys_<first hash byte hex>
   _<second hash byte hex>.index

 // contain group states 
 // like last kto index
 // using leveldb
 .state
 
 // lowest kto index, highest kto index
 // kto index = count, [file positions where transaction which contain kto starts]
 // sorted
 // write out after block finished, until than exist only in memory
 // hash at end
 blk0000000X.index 

 // size, serialized transaction [loop]
 // hash at end
 blk0000000X.data