* Improve extra requirement handling
* New mechanism to handle parameters beforehand in chained
calls, and the ability to get help on available parameters in chained
calls (through `?help`).
* Redefined Analysis, to reflect the new ontology
* Add parameters as an entity in the schema
* Update examples to include analyses and parameters
* Add processing plugins, with an interface similar to analysis plugins
* Update tests
* Avoid duplication in split plugin
Closes#51
Squashed commit of the following:
commit d145a852e7857784ba92efc556bb9e513ad5374b
commit 6a1069780b4a5cf26659134bcbea7a5fcec00ad7
commit ca69bddc17122e08142e93180d687d9b91cb4f1f
commit aa35e62a2724f9a3c33765d88de01fe8e44ba5f8
