JAV-90 conflicting transports in spring boot starters

[eric-lee-ltk]

resolved port conflict between tomcat and vertx.

1. extract EnableServiceComb Annotation and common dependencies of provider and transport to a new module named spring-boot-starter-servicecomb.
2. disable tomcat auto start when using vertx only in case of port conflict
3. now spring-boot-starter-provider provides vertx transport dependencies while spring-boot-starter-transport provides servlet transport dependencies.

Cautious: If we need both servlet and vertx to work under spring framework, please set application.properties to be spring.main.web-environment=true and avoid servlet and vertx using the same port, e.g. 8080.

[coveralls]

Coverage decreased (-0.01%) to 85.209% when pulling 19db726 on eric-lee-ltk:JAV-90_starter_port_conflict into 2afb8c2 on ServiceComb:master.