Improved fields CSV parsing

* trim excess whitespace (especially on Window, where \r\n is normal).
* allow different paths on non-Windows platforms.

The latter will probably investigated further when Mac OS support is
implemented.
Fix field-info loading
Fix length-delimited value parsing

As of a change (bug fix) yesterday, the code was accidentally parsing
values *after* the length-delimited value, instead of the value itself.

Easy fix.

Note, this breaks the google_message2.dat test.  Will fix that soon.
Fix embedded message parsing

There were a couple of issues, mostly around QByteArray's not being
destructively consumed, resulting in infinite loops.  The simplest
solution was simple to make all parse functions stream (QIODevice)
based.

Also fixed a bug with the readLengthDelimitedValue function not
returning an invalid QVariant on failure.
Add field info unit tests
Add some references