dont import main context in download context
dont import main context in download context

By importing the spring main context (intended to be shared
between wicket and other servlets) in the context for the
download servlet, <context:component-scan> is imported,
which finds components within a given package, and does
autowiring on them through an implied <context:annotation-config>.

However, the download-context is used for the download-servlet
by the dispatcher-servlet with the main-context as parent-context.

Importing the main-context in the download-context means the
component-scan is done twice.  This raises a warning that the
TapPU persistence unit name is already used, because the
org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean
is instantiated twice.

For this reason, declare the download-controller bean explicitly
with just a <context:annotation-config> to get the autowiring done.

An alternative would be to use <context:component-scan>, but
on a package that does not include the services detected by
the main config.

ekonijn/http-tap,ekonijn/http-tap