pom.xml

[NO ISSUE][OTH] Codegen clean up and plugin removal
- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Remove the codegen related files.
- Remove the codegen plugin.
- Remove the codegen plugin dependency from pom files.

Change-Id: I2c17f9f3f0c73f2ec3048a39da3cbbdd5f24e816
Reviewed-on: https://asterix-gerrit.ics.uci.edu/3396
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Hussain Towaileb <hussainht@gmail.com>