Add a note on maven filtering

This commit adds a documentation note explaining how to change
the delimiters used to filter maven tokens as these conflict with the
delimiters used by Spring (i.e. ${foo:default}).
Change order of config file locations to be more natural

The most natural order is "more specific locations win". That way
if a use has application.properties in the root of a JAR (as is
normal), overrides can always be made on
classpath:/config/application.properties (as well as
file:./application.properties which has always been the case).

Before this change properties in classpath:/config/* were over
written by those in the root location, not the other way round.

Fixes gh-527
Add dependency on spring-boot-starter-test

Fixes #530
Add missing JQuery and Bootstrap dependencies

Fixes #531
Add YAML syntax highlighting in docs

Also added JSON and tweaked properties settings.

Fixes gh-511
Rename `starter-shell-remote` to `starter-shell`

Fixes gh-462
Remove snapshot repos from starter parent

Fixes gh-419
Add missing datasource properties to refdocs

Fixes gh-504
Polish gradle examples

Spaces -> Tabs, version number, whitespace.