[Spring Boot] Added web support detection / force flag

Spring Boot web profile autodetection can be now overridden with the boolean system property `io.fabric8.process.spring.boot.container.web`. This option will be useful if user would like to override web nature of the process on the Fabric level (via fabric profile for example).

We can also explicitly set the web nature of the application on the `FabricSpringApplication` builder level.