RFR: 8091: Refactoring for jmc/application [v4]

[Christoph Langer]

> The sibling PR to #495 for the non-core project.
> 
> It cleans up the pom, bumping some versions and fixing URLs.
> The integration for spotless and checkstyle is cleaner now, allowing to build projects from subdirectories.
> spotless is called as part of the main build lifecycle now.

Christoph Langer has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Bunp spotbugs and ignore configuration directory that is created by spotbugs calls
 - Merge remote-tracking branch 'upstream/master' into JMC-8091
 - JMC-8091

-------------

Changes:
  - all: https://git.openjdk.org/jmc/pull/497/files
  - new: https://git.openjdk.org/jmc/pull/497/files/6dc2de93..8a2f2908

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=497&range=03
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=497&range=02-03

  Stats: 82 lines in 8 files changed: 68 ins; 0 del; 14 mod
  Patch: https://git.openjdk.org/jmc/pull/497.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/497/head:pull/497

PR: https://git.openjdk.org/jmc/pull/497