OPS-2114

[jenkins_common] update the seed_job.xml

TE-2548 Support for building Open edX release Docker images

Add declarative pipeline plugin and alphabetize list

Fix analytics name when calling play

Among other things, this will:

* Fix the "assignedNode" tag to allow this job to run on instances
  labeled "dsl-seed-runner".  Otherwise, this job will not run at all.

* Correct indentation for multi-line text areas, including
  "additionalClasspath".  Otherwise this job is guaranteed to fail.

* Update some hard-coded plugin versions, apparently.

Also cleaned up roles to plays to better indicate what they map to

[jenkins_build] Add the pipeline-utility-steps plugin

Remove Vagrantfiles for Open edX installations

Was trying to keep the play consistant with the role, but there were downstream
consumers (gocd) where underscores were not used so consistency was impossible.
Opting to go back to the way the play was previously named

The primary motivation is that this provides convenience functions for
parsing YAML files.

Move analytics-api to edx_django_service role

set dns_name for all sandbox runs

Estute/install and configure splunk plugin

TE-2546 Remove references to obsolete requirements files

Bump boto3 from 1.7.4 to 1.7.6

Bumps [boto3](https://github.com/boto/boto3) from 1.7.4 to 1.7.6.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](https://github.com/boto/boto3/compare/1.7.4...1.7.6)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Fix requirements for jenkins worker

revert splunk config work

Add environment token for id-verification faq page

add missing splunk hostname variable

add splunk config template to jenkins common

fix name of splunk config script