Added Timestamp class to simplify working with timestamps
Added CueSetting parsers for WebVTT cue-settings

Also added tests for these setters.
Fix warnings in WebVTTParser.cpp
Fix failing CollectTimingsAndSettings tests

The new MalformedTimestamp value is -1 milliseconds, but tests
enter -1 seconds. I let the test function do the conversion
automatically.
Implemented List container based on QList, with many enhancements

The similarities and differences are briefly outlined in TimedText/List.h.

They include:

 - No exceptions
 - Hidden/PIMPL'd private data.
 - No public unsafe operations
 - No assertions
 - STL-styled iterators (currently without iterator tags)

I've only implemented a very simple test suite, which conducts a
series of tests on primitive types. I'll be extending this as time
goes on.
Added tests for cue dispatch and retrieval

I've also created an EmptyCue type, which allows free initialization
with the default constructor. The EmptyCue is completely immutable,
and so the CueSettings tests had to be updated to construct an
actual mutable cue.
Fixed memory management in String class

Checking if d points to sharedNull more frequently now.
Merge pull request #8 from caitp/issue-8

Store and dispatch parsed WebVTT Cues to Client