Update README.md for 1.0.0 Alpha

(1) Update the https://github.com/mariadb-corporation/mariadb-columnstore-engine/blob/columnstore-1.0.0/README.md

Replace the entire content of the README.md with

"This is MariaDB ColumnStore 1.0.0

MariaDB ColumnStore 1.0.0 is the development version of MariaDB ColumnStore. It is built by porting InfiniDB 4.6.2 on MariaDB 10.1.10 and adding entirely new features not found anywhere else.
MariaDB ColumnStore 1.0.0 is an Alpha release. This is the first MariaDB ColumnStore release, not all features planned for the MariaDB ColumnStore 1.0 series are included in this release. Additional features will be pushed in future releases. Do not use alpha releases on production systems."

(2) Remove https://github.com/mariadb-corporation/mariadb-columnstore-engine/blob/columnstore-1.0.0/InfiniDBContributorAgreement.pdf