Add license-maven-plugin and some default license merges

[jbonofre]

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[jbonofre]

R: @davorbonaci

[coveralls]

Coverage decreased (-0.01%) to 69.676% when pulling 5bede0a on jbonofre:licensing-fixups into 80c86f8 on apache:master.

[davorbonaci]

LGTM

(please self-merge)