Fix GETting multi-row values

[olapiv]

• Always check errors using getNdbError()
• Compare hashes in bash tests instead of full values
  FIXES:
• Multi-value-row fetching: use different memory for each row
• Multi-value-row fetching: use clean struct for every fetch (place fetch into separate func)
• Calculate number of value rows correctly in SET
• Using uint8 for type safety when read/writing value lengths from buffers
• Usage of auto-increment for rondb_key; use SQL's AUTO_INCREMENT