[MARCHETYPES-78] Update default Java version in archetype projects to 1.8

[judovana]

Based on "discussion"

Based on the "discussions" in:
https://lists.apache.org/thread/chqcxvlko3nz6cgrs2kzjrdy5tv9spkx , #22 , #20 , #18

bumping default jdk of all archetype projects to 1.8.
This expects #23 to be emrged first. ig n ot, it shoudl be rebased.
Note that the test in maven-archetype-quickstart now do not have sense. As there was not a agreement that the test shuold be changed, it will be done in separate PR

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