Workaround for AOT protocol bug with getStackTrace

When creating an uberjar, the code gets AOT compiled. When type
hinting the .getStackTrace call, it returns an array. That array
caused us to hit https://dev.clojure.org/jira/browse/CLJ-1790. This
commit works around that until we upgrade to Clojure 1.9.

Update metabase-head jdk version to java 8

Clean up some indentation and other code

Backported improvements from sync refactor branch

* non blocking database deletion

keeps track of database deletes by adding them to an array when the
delete starts and then removing them when the API tells us the delete is
done. allows us to show deletion status.

* add test

* lint

* cleanup [ci e2e]

Fix MySQL & Postgres tests on localhost w/o password

* hide action popover when scrolling data table

* flow

* add instance method for action hiding

Presto driver multi-aggregate and fixes

Refactor reference guide

fix typo in setup.clj

Unify test application db environment variables [ci drivers]

Rename functions with µ to microseconds [ci drivers]

Explicitly load driver code and fail tests when driver is present

* allow for auth specific admin setting 'subroutes'

* remove toggle

* add breadcrumbs

* better name for options component

* add tests

make create test async

add goBack utility

test click paths

The unicode character in the function name can cause problems with AOT
generated class names that have that µ in the filename. On some users
systems if this isn't encoded properly it can replace the µ with a ?
and cause failures compiling metabase.

Fixes #4441

Fixed driver installation description.