Explicit parameter generation syntax in templates

- Add "generate" field to specify generator to be used
- Add "from" field to specify the input value for generator
- Remove "type" field, as it's always "string" anyway
Move test etcd to _output, remove third_party folder
Issue #177: Use $(uname) instead of $OSTYPE
switch to openshift-registry and add pullimages script
Merge pull request #181 from VojtechVitek/explicit_generators_syntax

Merged by openshift-bot
Merge pull request #189 from bparees/switch_registry

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Add doc on images
Merge pull request #197 from ncdc/add-images-doc

Merged by openshift-bot
Fixing typos
Merge pull request #198 from danmcp/master

Fixing typos
Merge pull request #194 from VojtechVitek/uname_ostype

Merged by openshift-bot
Merge pull request #188 from liggitt/remove_third_party

Merged by openshift-bot