Some dependency hygiene and update to Boot 1.5.10

The web module doesn't really need to depend on tomcat and all of
the Spring Boot web stack, but users need a way to grab that stuff
quickly if they want it (hence the new starter).

Also removed all spring-boot-starter dependencies from core and
context modules.

spring-cloud-starter-function-web/src/main/resources/META-INF/spring.provides

@@ -0,0 +1 @@
+provides: spring-cloud-security