Enhancement: abc import should report indexing failures

[siddharthlatest]

abc import logs currently don't show the number of records that failed to index. This behavior can be easily supported as the underlying bulk API reports the failures.

A sample output line for this can be:

• When there are failures: 10 out of 4654 total records failed to index
• When indexing succeeds: 4654 total records indexed.

Note: We only report total records when a data source import is divided across multiple bulk requests. We should correspondingly also report total failures per import command.

Version Info:
Version: 1.0.0-alpha.0
Variant: !oss
Go version: go1.11.10
OS: linux
Arch: amd64