chore(webapp): move webapp to separate repository

camunda-webapp moved to https://github.com/camunda/camunda-bpm-webapp
chore(distro): remove lib folder from jboss distro

- redundant with the modules folder
feat(engine): add script as possible task listener

related to #CAM-2361
refactor(UI-TEST): implement page objects

This commit refactors the webapp UI test suite for page object
introduction.
test(UI-TEST/admin): add groups page tests
test(UI-TEST/admin): add admin user setup test
refactor(UI-TEST/admin):improve object instatiation

introduced index.js files for each group of page objects