Decommission of static analyzers

[php-coder]

• [x] CheckStyle
  • [x] remove CheckStyle: ignore and @SuppressWarnings("checkstyle:*") comments
  • [x] #260
  • [x] #1015
• [x] PMD
  • [x] remove @SuppressWarnings("PMD.*") comments
  • [x] #195
  • [x] #261
  • [x] #1018
  • [x] #1250
  • [x] #1646
• [x] sortpom
  • [x] #1174
• [x] boolint
  • [x] #316
• [x] rflint
  • [x] #1104 need to decide what to do
• [x] shellcheck
  • [x] remove shellcheck disable comments
  • [x] #1615
  • [x] #710
• [x] html5validator
  • [x] #541
  • [x] #760
• [x] ansible-lint
  • [x] #1144
  • [x] #1515
  • [x] #1570
• [x] CodeNarc
  • [x] remove @SuppressWarnings from Groovy code
  • [x] #508
  • [x] #539
  • [x] #994
  • [x] #1187
• [x] SpotBugs
  • [x] #480
  • [x] #1190
  • [x] #1198
  • [x] #1258
  • [x] #184
  • [x] #185
• [x] ErrorProne
  • [x] #999
  • [x] #1069
  • [x] #1235
  • [x] #1440
  • [x] will help to resolve #1350
• [ ] update decisions log: mention removal of error-prone and added workaround (see bb4afedd7b90f015fec4b951be13c0679690875a)
• [x] no need to add other static analyzers
  • [x] #183
  • [x] #422 looks useful, let's keep it
  • [x] #585
  • [x] #613
  • [x] #614
  • [x] #799
  • [x] #1062 looks useful, let's keep it
  • [x] #1201
  • [x] #1202
  • [x] #1203
  • [x] #1212 looks useful, let's keep it
  • [x] #1109 looks useful, let's keep it
• [x] #574 will have a lesser scope

maven-enforcer-plugin, probably, can stay altogether with maven-license-plugin.