Option to prevent name conflicts in `px:create-audio-fileset`

Add an `anti-conflict-prefix` option used to prevent name conflicting
in the audio files in the creation of the audio fileset.
Group the skippable elements by packets of 10

Group skippable elements instead of putting them all in one single
sentence, so that the audio buffers won't grow too much.

Also:
- Fixed regex group capture that made skippable elements to range only
  from 0 to 10.
- Added tests
- In the tests: changed some paths that were not synchronized with the
  current version of text-to-ssml
Merge pull request #18 from daisy/memfriendly

Close #18
Update POM versions to 1.9-SNAPSHOT
Use different threads for TTS and encoding

- Major change: TTS and encoding no longer run in the same threads.
  Corrolary: big PCM chunks are kept in memory and a new class helps
  track allocations of audio buffers;
- TTS processors no longer write in the Thread's big audio buffer with
  a moving offset. The processors return lists of buffers instead;
- The timeout class no longer creates a new thread every time they are
  enable;
- The AudioBuffer class has been moved to audio modules;
- It is now possible to run 3 simultaneous synthesis without blocking;
- ATTBin is no longer supported (will be deleted soon);
- Acapela adapter looks for libnscube64.so on 64bit platforms.

Non-backward compatibility for:
- ssml-to-audio
- tts-common
- tts-adapter-acapela
- tts-adapter-espeak
- tts-adapter-sapinative
- tts-adapter-osx
- tts-adpater-attnative
Use XSLT to prepare SSML for TTS processors

- XSLT is now used for transforming SSML into what must be provided as
  input to the TTS processors, instead of in-house SSML serialization;
- The TTS processors that cannot handle marks do no longer split SSML
  themselves. It is now done in the threads that call the TTS
  processors, and they transform SSML into SSML, rather than text;
- The marks are now mutable, as they are stored in a dedicated class,
  instead of map entries;
- Use Iterables instead of Collections when the PCM chunks are
  concatenated;
- Fixed a leak when a MemoryException occurs.

Fixes #6
Needs the branch `xslt` of `pipeline-framework`.
Minor fixes to `SSMLtoAudio`

- Small improvement to make it less likely to reach a memory consumption peak ;
- Fixed a mistake in the info printed about the encoding memory footprint.
Store temp audio files in the right directory

Fixed a bug that made temporary audio files to be stored in the wrong
directory.
Improve Acapela adapter and TTS exception report

- Make Acapela adapter work with a mixed of working/non-working voices;
- More details printed for Synthesis exceptions.
Update POM versions
Merge pull request #15 from daisy/fast

Close #15
Add VoiceManager and support voice gender

- Voice selection based on speakers' gender
- Tests for the TTS Registry
- Bit of refactoring to separate the TTS Registry from the Voice managment
Identify approximate voice matches

- Added a boolean to the voice matching functions to know whether
  successful matches are exact or approximate. New errors/warning have
  been added to notify the users.
- Fixed a bug that made impossible some kind of approximate matches.
Improve voice selection when no exact match is found
Allow running XSLT SSML adapters from different XProcRuntime

Changed the location where the XSLS SSML adapters are stored so as to
make it possible to run them from different XProcRuntime.
Merge pull request #21 after rebase

Close #21
Make CSS speech inlining a dedicated step

- New workflow: removed the CSS speech inlining from the main TTS step.
  It is now in a separate step.
- CSS inlining enhancement: make it possible to use relative URIs for
  cues in all the CSS stylesheets, and prepare for the possibility of
  using embedded CSS
- The Java step produces a cleaner output so that it can be plugged
  into a validator or something else in the new workflow
- The non-aural CSS properties are no longer inlined.
Introduce a single config file for CSS and lexicons

Use a single config file for the CSS and the lexicons, instead of
string options.
Preserve the input default NS during CSS inlining
Enable custom structural announcements with SSML

Insert custom SSML annotations so as to clarify some elements (e.g. table, lists etc.)