add release notes for 2.1.8 (pingcap#1305)

add 2.1.7 changelog (pingcap#1294)

add 2.1.6 release notes (pingcap#1196)

tispark-2.1.5 release notes (pingcap#1090)

Remove useless dependencies (pingcap#1075) (pingcap#1080)

release tispark-2.1.4 (pingcap#1068)

release tispark 2.1.3 (pingcap#1026)

fix view parsing problem (pingcap#953) (pingcap#964)

(cherry picked from commit 0fb1b6f)

Add base data type suites and schema/data generator (pingcap#939)

release 1.2.1 (pingcap#901)