Added an early-out when Enqueuing if the input filename is blank or the file doesn't exist.
Added additional File.Exists checks before attempting a new FileInfo() when processing the queue and moved these checks inside try/catch (in case the file was deleted since the early out).
Added try/catch protection for the instant playback path as well.
Added a new AudioOptions parameter class to control whether or not the file is deleted after playback. (Unconditionally deleting files, which was intended for NativeVoice audio caused problems for Herald and it's local cache.) These options are also exposed to plugins.
Tidied up a bunch of UI misalignment (which will likely cause conflicts with #169 ).
...to avoid breaking audio playback entirely.
File.Existschecks before attempting anew FileInfo()when processing the queue and moved these checks inside try/catch (in case the file was deleted since the early out).