Finalize ParticleSystem, add angular velocity, multiple emitters, GetBool for IDataReader, use Lerp in LerpColor.

Voile/Source/Resources/DataReaders/IDataReader.cs

@@ -30,6 +30,13 @@ namespace Voile.Resources.DataReaders
     /// </summary>
     public interface IStreamKeyValueGetter
     {
+        /// <summary>
+        /// Get a boolean from this data getter.
+        /// </summary>
+        /// <param name="key">Key of the value.</param>
+        /// <param name="defaultValue">Default value in case this getter fails to get data.</param>
+        /// <returns></returns>
+        bool GetBool(string key, bool defaultValue = false);
         /// <summary>
         /// Get an int from this data getter.
         /// </summary>