Refactor parameters.py
Refactor parameters.py

Converted all relevant functions to use helpers.<insert function>
instead of a specific import.

Added commas to last entries of mapping tuples.

Signed-off-by: Tan Heng Yeow <e823c569ecd97d7c59d0e90eefc0aeb98a922c4d@u.nus.edu>
Change-Id: Ie7c40809ad8259fc3906871360c16dbb6e58a4b0

gforcada/jenkins-job-builder,wsoula/jenkins-job-builder,gforcada/jenkins-job-builder,gforcada/jenkins-job-builder,puppetlabs/jenkins-job-builder,gforcada/jenkins-job-builder,puppetlabs/jenkins-job-builder,gforcada/jenkins-job-builder,puppetlabs/jenkins-job-builder,wsoula/jenkins-job-builder,puppetlabs/jenkins-job-builder,wsoula/jenkins-job-builder,wsoula/jenkins-job-builder