Fix ordering problem in PropertySourcesPropertyValues

This affected @ConfigurationProperties binding whenever there
were multiple PropertySources (from any source) in the
Environment and mor ethan one carried a value for a particular
key. The rules for override are clear in Environment.getProperty()
but they were being violated by the PropertySourcesPropertyValues.

Fixes gh-916
Use the ServerProperties to add prefixes to paths

when server.servletPath is set we need to add prefixes to
the security filter paths.

Fixes gh-945