Split code to Maven modules

[php-coder]

After split to packages by features (#927), we can extract some features to separate Maven modules that produces JAR files.

Tasks:

• read https://www.baeldung.com/maven-multi-module
• read https://www.baeldung.com/spring-maven-bom
• read https://maven.apache.org/guides/mini/guide-multiple-modules.html
• read https://spring.io/guides/gs/multi-module/
• fix Travis build:
  • fix "TemplateInputException: Error resolving template "error/403", template might not exist or might not be accessible by any of the configured Template Resolvers"
  • fix license plugin failure
  • fix bootlint failures (update bootstrap)
• don't use Spring as a parent (see https://docs.spring.io/autorepo/docs/spring-boot/1.5.8.RELEASE/reference/html/using-boot-build-systems.html#using-boot-maven-without-a-parent)
• extract all plugins to a parent pom (do we really need this?)
  • checkstyle
  • pmd
  • license
  • sortpom
  • jasmine
  • enforcer
  • surefire
  • codenarc
  • findbugs
  • failsafe
• update wiki docs