Develop/cdk constructs

[itzhapaz]

Issue #, if available:

Description of changes:

• Changed the step functions implementation to workflows where a you can set one or more workflows for demo or your own.
• Add a first workflow of variant calling using gatk HaploTypeCaller (fastqc -> bwa mem -> samtools sort -> picard AddMissingGroups -> samtools index -> gatk HaploTypeCaller)
• Add AWS batch json examples to run multiple tools
• Added the option of changing the "genomics" prefix for ecr and the templates to a custom name and defaulting to "genomics".
• Updated the UserData content to replicate the one from the CloudFormation templates
• Removed the onDemandComputeEnvironment from the defaultQueue

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