Revert "Support Java 8."
Revert [#1800] Update compiler for support to java 8

This reverts commit 3d604052ab2e83c0913244f3782a6f369e143d27.
This reverts commit 3d3c3fe45733147f5478a70bd58891f163647f51
This reverts commit e9d80946f4198bc7239f506e76e54c3c40470193
This reverts commit 4521b8026b13ada18439120af2f8a4e8a79b7471
This reverts commit 021d275545b76ebac43be623143ec85fe7f52119
This reverts commit 3b7d7be90cfac1f60e722aacca577e8f5da25ef5