Put images in loading/init screen

This commit adds support for adding dimensions to existing
fields. Values and human readable values (optional) can also be
added/updated.

This commit adds storage of dimension data that the user provides for
an existing field. This is to translate enum-like
fields (i.e. integers) to a textual description of that data. This
remapped value will be included in the response with the original
value. The UI will then take that and show the more user friendly
remapped value.

The new "remapped_from" and "remapped_to" attributes in the cols field
of the response will indicate that a field replaces another field.

* add image files and get new text in there

* modal content + refactor

* update illustrations and remove redundant one

* add tests

* add images

* button text tweaks

* padding

This commit adds new min/max metadata to all numeric columns. That
metadata is used in the automatic binning of breakout fields. This
commit also extends MBQL to indicate that a breakout column (or
columns) should be binned using a "default" strategy. The query must
also include the maximum number of bins. Using the number of bins with
the min/max values, the bin width is computed and used in the SQL
query to group data.

https://github.com/metabase/metabase/issues/3715
Liquibase has been rechecking the jar signature for each migration
file, resulting in slow startup times.