Changed README to document new structure

README

@@ -10,10 +10,36 @@ What is GTSAM ?
 
 GTSAM is not (yet) open source: See COPYING & LICENSE
 
-Directory structure:
+The code is organized according to the following directory structure:
 
-  cpp	  C++ source 
+  base				provides some base Math and data structures, as well as test-related utilities
-  matlab  MATLAB proxy classes and wrappers
+  geometry		points, poses, tensors, etc
+  inference		core graphical model inference such as factor graphs, junction trees, Bayes nets, Bayes trees 
+  linear			inference specialized to Gaussian linear case, GaussianFactorGraph etc...
+  nonlinear		non-linear factor graphs and non-linear optimization
+  slam				SLAM and visual SLAM application code
+  
+All of the above contain code and tests, and build local shared libraries that are then
+bundled in a top-level shared library libgtsam.la. After his is built, you can also run
+the more involved tests that test the entire library:  
+  
+  tests				more involved tests that depend on slam
+
+Furthermore the MATLAB wrapper generator code is run as well
+
+  wrap				MATLAB wrapper generation code
+	gtsam.h			interface file for which wrappers will be generated
+  toolbox			MATLAB proxy classes and wrappers generated
+  matlab			examples and tests of the above  		
+
+Finally, there are some local libraries built needed in the rest of the code:
+
+  colamd			COLAMD and CCOLAMD by Tim Davis needed for re-ordering
+  CppUnitLite	unit test library
+  doc					documentation
+  ldl					LDL by Tim Davis (will probably go)
+  m4					local M4 macros
+  spqr_mini		Core frontal solver from SuiteSparse (will probably go as not LGPL)
 
 
 Boost Dependencies: