Update HISTORY for 1.7.2

Update version number for 1.7.1 release

Update HISTORY and version number for 1.7.0 release.

Merge pull request TileDB-Inc#1397 from TileDB-Inc/ttd/backport-schema-h

Backport fix to 1.6.3

Update HISTORY.md and version numbers for 1.6.2.

Add HADOOP_VERSION variable, and bump to 3.1.2 to try to fix download…

… failure

(cherry picked from commit 56ec1b7)

Update HISTORY.md and doc links for 1.6.0.

Update version numbers to 1.5.1

Update HISTORY.md and example links for 1.5.0 release.

Bump version to 1.4.2