Fix time-domain calculations of the optimal observation filter

The calculations for the time-domain optimal observation filters have been fixed.

There are some minor improvements in other fields such as:

• A bug in obsFiltTD() that screwed up the dimensions of the arrays when there was only one source.
• A bug in ptSrcFieldTD() that screwed up the dimensions of the arrays when there was only one source.
• The virtual microphone geometry generation function was heavily modified, and its interface has changed.

This merge closes the Closes #8 (closed).

Sound Fields/MATLAB/Functions/ptSrcFieldTD.m

@@ -170,7 +170,7 @@ function [rSig, rSigMean, rSigMtx, rSigMtxMean, Q] = ptSrcFieldTD(sPos, rPos, fs
     end
 
     % Sum source signals at each receiver position
-    rSig = squeeze(sum(rSigMtx, 3));
+    rSig = reshape(sum(rSigMtx, 3), size(rSigMtx, 1), size(rSigMtx, 2), size(rSigMtx, 4));
 
     % ====================================================
     % Calculate output arguments