Switch vogar to use Jack and 1.8 language features by default

Default is now --toolchain jack --language JN instead of
--toolchain jdk --language J1_7.

The vogar script now picks the ALPHA version of Jack by default
since that is the one being used in the platform build.

Bug: 27376034
Bug: 20705484
Bug: 26753820
(cherry picked from commit 3cdb4296d00bf9294b6d4705e5a7b6742d7e6148)

Change-Id: I29c9f4d88c193d6d1f08a1cc514e691b5e5a7476
2 files changed