changed debug array tree to print string key
Merge branch 'master' of https://github.com/ThankyouSoft/nldb
Fix for an issue that keys in a split internal node not getting propagated.
1) Show keys as string format in debuggable_array_tree if key size is greater than 16.
2) Show first 8 bytes as an integer if the key size is 16.
3) If an internal node splits, propagate key count of the split node up to any split parent.