Fix issue 547 (Schematron ignores context select) and 548 (Schematron ignores AVT)

[AirQuick]

This pull request derives from #546. So needs to be handled after that.

---

Fixes #547
Fixes #548

The root cause of the problems is that in order to create a context document node, schut-to-xspec.xsl just copies child::node() to an external XML file and specifies the XML file as @href:

xspec/src/schematron/schut-to-xspec.xsl

Lines 68 to 81 in c84e19f

	<xsl:template match="x:context[not(@href)][
	parent::*/x:expect-assert | parent::*/x:expect-not-assert |
	parent::*/x:expect-report | parent::*/x:expect-not-report |
	parent::*/x:expect-valid | ancestor::x:description[@schematron] ]">
	<xsl:variable name="file" as="xs:anyURI" select="resolve-uri(
	concat('context-', generate-id(), '.xml'),
	concat($test-dir-uri, '/'))"/>
	<xsl:result-document href="{$file}">
	<xsl:copy-of select="./node()"/>
	</xsl:result-document>
	<xsl:element name="x:context">
	<xsl:attribute name="href" select="$file"/>
	</xsl:element>
	</xsl:template>

This pull request fixes it by creating a document node on memory at run time.

• 64fa045 reproduces Schematron ignores AVT #548: Travis, AppVeyor
• 6bcdefb reproduces Schematron ignores x:context/attribute(select) #547: Travis, AppVeyor
• 96f4de6 fixes the problems

As a bonus,

• test-dir-uri parameter in schut-to-xspec.xsl is no longer necessary. xsl:param in schut-to-xspec.xsl and its related lines in CLI and Ant have been removed.
• A pending test in test/schut-to-xspec.xspec is now activated.

[AirQuick]

@cirulls
Merged this bug fix.