Upgrade java.jdbc to 0.7.5

There are some nice performance improvements in 0.7.4, so updating to
the latest to benefit from them.

Upgrade Toucan to 1.1.2 [ci drivers]

Fix small i18n typos

Fix excessive DB calls on reference guide

Before this commit, via the `/database/:id/metadata`, we make a DB
call for each field's target table. On databases with a larger number
of these values, it can cause many database calls. This will fetch
them via batch hydration first, which will significantly reduce the
number of calls.

Mongo 3.6 support

Change database sync and field values job scheduling [ci drivers]

GA sync fixes 

Stream all JSON responses [ci drivers]

Previously we configured each database to have separate trigger + job
instances for sync+analyze and field values scanning. We were using
the default threadcount and "do nothing" upon misfires. This resulted
in a race condition like below.

By default, sync and field-values scans are scheduled at 50 minutes
past the hour (two separate jobs). As an example assume we have 10
databases configured. This would result in 20 jobs firing at 50
minutes past the hour. The order of execution of these jobs is not
defined. By default, we have 4 threads to execute these jobs. If the 4
threads are busy when a trigger occurs, it will wait up to one
minute (the default). If it can't get a thread in 1 minute, it will
misfire. The policy we had setup will discard the job when it
misfires. The end result of this is a race condition where we could
potentially not run sync on many databases and also be running 4 scans
or syncs at the same time, potentially causing memory issues.

This commit switches to a single job for sync and a single job for
field value scans. Every database will have a trigger for sync and a
trigger for field values, but only 1 instance of sync and field values
scanning will run at a time. In the event of a misfire, it will
execute it as soon as it's able and only once.

Driver simplification part 1 [ci drivers]

Keep using --add-modules=java.xml.bind flag for SQLServer driver

Fix issue with joins in BigQuery driver

Add a deprecation warning for JDK 7

This commit switches from `ring.middleware.json/wrap-json-response` to
a new function that will stream JSON responses. Before this change the
full JSON response was serialized to a String first, then written to
the response stream. This change will skip that step and write the
response to a PipedOutputStream directly.

This is the same approach that was used in the response for the
`/database/:id/fields` route, just generalized and applied to all
routes.

Merge branch 'fix-bigquery-joins' of https://github.com/jvdweerthof/metabase into jvdweerthof-fix-bigquery-joins-3

Add new test util with-temp-db-vals macro; remove resolve-private-vars

trim user name before set

Use JodaTime to parse datetime strings

Dashboard Text Cards

Minor code cleanup