Add exploded mode support in spring-boot

[jbonofre]

Right now, Minho only supports repackaged spring boot application jar, wrapping all jar in uber jar. Then, Minho uses JarLauncher to launch the spring boot application.

However, this is not the running mode recommended by spring boot. Minho should support running spring boot application in exploded mode (similar to spring-boot:run maven goal).

It means that Minho needs:

• to scan @SpringBootApplication annotation to find the Main class
• to have a way (using spring boot app pom for instance) to find all dependencies to populate the classloader, leveraging Minho tooling for instance
• don't use JarLauncher but create classloader and run instead

This preparation step should be performed at build time (in Minho tooling), not at build time.