Allow for creation of objects without JSON

node-group-template-create, cluster-template-create, cluster-create only work by accepting a json representation of the object

it should be possible to create these objects without needing json

--- ideas from original cli implementation bp ---

1. Simple example:
savanna cluster create
    -p apache_hadoop_1
    -t nn+jt m1.xlarge 1
    -t dn+tt m1.medium 5
    -n apache-hadoop-cluster-name-1

2. Using short flags:
savanna cluster create
    -p apache_hadoop_1
    -c apache_hadoop_no_compression
    -t nn+jt m1.xlarge 1
    -t dn+tt m1.medium 5 config=”common.huge_memory_reducer=true” # yaml
    -t dn+tt m1.medium 2 config=”tasktracker.http.threads=42” # yaml
    -t tt m1.large 10 tt_custom_template
    -n apache-hadoop-cluster-name-1

3. Using long flags:
savanna cluster create
    --plugin apache_hadoop_1
    --cluster-template apache_hadoop_no_compression
    --template nn+jt m1.xlarge 1
    --template dn+tt m1.medium 5 config=”common.huge_memory_reducer=true” # yaml
    --template dn+tt m1.medium 2 config=”task_tracker.heap_size=128m” # yaml
    --template tt m1.large 10 tt_custom_template
    --name apache-hadoop-cluster-name-1