SSP-1888 Refactor most Maven filtering to runtime config

Everything that was previously set in ./filters/local.properties and
thus injected into the application at build time can now be set in
any number of other files and thus be evaluated at runtime, most
notably {SSP_CONFIGDIR}/ssp-platform-config.properties.

Defaults which were previously in ./filers/local.properties are now in
uportal-war/src/main/resources/properties/ssp-platform-config.default.properties.
The only file which is still eligible for build-time property
placeholder resolution is
uportal-war/src/main/resources/properties/build.properties which is
specifically intended to reflect attributes of the build.

Historically, uPortal did evaluate some configuration at runtime.
For example: rdbm.properties, security.properties, and
portal.properties were all loaded by a
PropertySourcesPlaceholderConfigurer and could thus have their values
injected into Spring Bean definitions. Additionally, components
such as InitialSecurityContextFactory and PropertiesManager would
themselves read and expose subsets of properties in those files via
various APIs. The latter components would not, however, participate
in the same recursive property placeholder resolution that
PropertySourcesPlaceholderConfigurer supports. This patch fixes that
asymmetry.

Note that while the PropertySourcesPlaceholderConfigurer still
errors out during its initialization if any Spring Bean definitions
contain unresolvable placeholders, the dependencies from
PropertiesManager and other components that read properties files
directly are such that they will continue to behave as they have
historically and simply echo unresolved placeholders.

Tests are all in QueryablePropertySourcesPlaceholderConfigurerTest,
which is sightly overbroad in that in also tests
PropertiesManagerInitializer, but this was done because all the
tests are really focused on integration tests of the new capabilities
introduced by the former.

Some config files still don't participate in runtime property
resolution at all, notably PAGSGroupStoreConfig.xml.

This patch also moves the 'CAS Validate Filter' configuration out of
./uportal-war/src/main/webapp/WEB-INF/web.xml and into
./uportal-war/src/main/resources/properties/contexts/mvcContext.xml.
This was done to allow that configuration to participate in runtime
property placeholder resolution. Unfortunately, we could not use the
standard DelegatingFilterProxy by itself because some of the
config being set on the Filter has to come from FilterConfig and
can't be set using simple Spring Bean properties. The workaround is
DelegatingFilterProxyBean, which allows a Spring-configured Properties
collection to masquerade as name-value config pairs on a FilterConfig
instance.