Clean PDF plug-in stylesheet

* Remove obsolete comments
* Add datatypes
Fix build script to work with new docs build
Add datatypes to variable and template in mappull XSLT
Move message configuration file to dost-configuration.jar

The messages.xml file should not be included in dost.jar as it is not
regenerated during integration. The dost-configuration.jar is intended
for configuration files and files that are generated during integration.
Treat missing filter file as a fatal error #1703
Fix plugin JAR compilation classpath configuration
Run JUnit tests from Ant like in Maven
Add Ant libraries to Ivy dependencies

This allows running dita command directly after building JARs and
running the integration process, without needing to define an external
CLASSPATH system variable.
Move messages.xml to resources
Fix messages.xml relocation in XSLT
Merge HTML5 improvement and WAI-ARIA support #1819
Add Ant target for building JARs and running integrator

Default target in Ant changed to "build". This runs JAR generation
and runs integrator.
Support file extensions other than .xml and .dita
Add src attribute to job configuration

The src is the absolute URI to the source document for a fileinfo.
Processing has been changed to rely on this and contains initial code
for customising temporary file URIs.
Separate temp file name generator to a separate class
Refactor uplevels to support alternative temp directory names

Update uplevels processing to allow generating e.g. flattened temp
directory structures.
Accept all non-DITA or image references #1687

All references from image elements are treated as images references
without configures file extension. All references to non-DITA files
are processed without configured file extension.
Fix common attribute procession in dlentry
Merge README updates #1825
Remove deprecated error messages #1800