fix name of licence file licence.txt => LICENCE
fix duplicated compiler plugin configuration in integration tests pom.xml

also, format pom.xml files
[#17] add dependency and configuration for licence-maven-plugin
[#17] no license check in packaging module but version must be set

if version is not set in package module, default version (1.7) will be used which does not have format goal => running mvn license:format on project fails on packaging module
[#17] exclude license and documentation (.md) files
[#17] add or update license header in the whole project