Upgrade build train CI pipeline to multi-stage (microsoft#90)

* add staged pipeline

* remove release id

* remove train in release pipeline

* revert to BASE_NAME vars

* Move train trigger to new stage

* cleanup register comments

* add conditional for triggering train pipe

* update doc steps

* string vs boolean

* var to boolean

* set to false

* try with true

* cleanup images

* Use Coalesce so override works

* add back build artifacts

* address feedback

* include code/scoring path for ci

update conda dependencies (microsoft#93)

* update dependencies

* cleanup spaces

enable App_Insight (microsoft#86)

Update getting started docs. (microsoft#82)

Update Badge, Pipeline filters (microsoft#81)

* Update current build badge

* Only trigger Dockerfile change

* Include iac pr filter

Training a model with R on ML Compute and Databricks (microsoft#77)

Remove app secret from log (microsoft#70)

Fixed typo in code filename (microsoft#71)

typo fixed (mlservice to ml_service) (microsoft#69)

Updated repo to use the SDK more consistently (microsoft#67)

* Updated code to use SDK instead of JSON files

* include location in environment setup

* docs updates

* Update docker-image-pipeline.yml for Azure Pipelines

* Update docker-image-pipeline.yml for Azure Pipelines