allow xsl:params in Schematron 

It was asked on [xproc-dev](http://lists.w3.org/Archives/Public/xproc-dev/2014Apr/0000.html) whether it was possible to could pass parameters to Schematron `let` declarations. While this is not possible, I sketched a way how to allow foreign markup in Schematron and use `xsl:param` within the Schematron. 
While `xsl:*` may already be enabled by passing the parameter `allow-foreign = 'true'` to the `p:validate-with-schematron` step, the step’s parameters won’t currently propagate to the final pass, when the generated XSLT is applied to the document. 
So I suggest that we supply the same parameters also to the final pass.
The spec doesn’t seem to disallow this; it is kind of fuzzy on this whole parameter thing in `p:validate-with-schematron`: “The parameters port provides name/value pairs which correspond to 
Schematron external variables.”
Fixed issue #147 for POSTs to /pipelines/{id}

Issue may still exist for POSTs handled by
- com.xmlcalabash.piperack.Input
- com.xmlcalabash.piperack.Option
- com.xmlcalabash.piperack.Parameter
Fixed #147 in Input, Option, and Parameter classes
Refactor XPath compilation to fix issue #143.
Updating Saxon to 9.5.1.5
Merge pull request #151 from jwcranford/fix147

Fix #147 in Pipeline, Input, Option, and Parameter classes. Use the entity media type not the variant.
Merge pull request #146 from gimsieke/patch-2

Pass parameters on p:validate-with-schematron to all Schematron phases.
Merge pull requests #151 and #146 into my Saxon 95 dev branch
XML Calabash version 1.0.17-95 released
Bump version number
Fixed issue #152 by replacing thread local variable with (threadsafe) singleton registry.
Support using the Validator.nu serializer for HTML; fixes issue #150
Fix issue #153; don't reset the base URI if the override base URI is the empty string
Fix bug (reported by Oxygen) where using the API to write a document resulted in an attempt to write to a closed handle
Fixed docs build process to work with the new double-repo approach
XML Calabash 1.0.18-95 released
Copy antlib.xml into jar file to fix issue #157
Make application/pdf the default content type for the CSS formatting step
Make failure to instantiate a requested extension function more obvious
Add a cx:version attribute to the p:validate-with-xml-schema step
to specify the schema version.