[general] Add maven-enforcer-plugin

[bigscoop]

• Added maven-enforcer-plugin for all modules in order to automatically check dependency tree for inconsistencies
  For now there are 3 modules that do have unresolved inconsistencies, there the maven-enforcer-plugin is temporarily disabled. Will create corresponding issues and analyze the problem later.

• Fixed

Warning:  The project org.knowm.xchange:xchange-parent:pom:5.1.2-SNAPSHOT uses prerequisites which is only intended for maven-plugin projects but not for non maven-plugin projects.
For such purposes you should use the maven-enforcer-plugin.
See https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html

by moving the prerequisite to maven-enforcer-plugin

• Updated minimal required maven version