minimal jsonschema validation
remove environment from top level jsonschema
define parallelBy
define inputs

* inputType is defined recursively to support nested_parallel_by_operation_matrix_inputs
* these messages are here instead of in a comment because json doesn't support comments
define tasks
define edges
define methods
define execution parameters as inputDictionary
add some minItems and minProperties constraints

Not sure if these are correct.  Setting them to generate a discussion about
what the correct values should be.
remove types for inputs and parameters
use `items` instead of `patternProperties` to enforce type of items in taskDictionary
taskDictionary must contain at least one task

Therefore the edgeList must contain at least two edges
Merge branch 'master' into validate_posted_schemas
Merge pull request #69 from mkiwala/validate_posted_schemas

Validate posted schemas