====== Complex Matrix class ======

As of Auryn v0.8 the library comes with a complex matrix class which generalizes [[SimpleMatrix]] to synaptic connections which can have more than just a single scalar value per connection. [[ComplexMatrix]] is essentially a rank three tensor class optimized for sparse synaptic transmission.

More specifically, like SimpleMatrix the complex matrix class implements a sparse matrix that allows fast access of all elements of one row. It provides row iterators to efficiently propagate
spikes. Memory has to be reserved when the class is defined and elements can
only be inserted row by row starting from "top left to bottom right". This scheme enables
related data fields to reside in memory next to each other.

ComplexMatrix generalizes SimpleMatrix to a rank 3 tensor in which each
synaptic connection can have more than one value (third tensor mode --
corresponding to a synaptic state). This allows to efficiently implement state
based complex synaptic models which have their own internal dynamics. 
Instead of storing all synaptic data values in one long array the synaptic
state values are stored in multiple state vectors which can be manipulated
efficiently in a vector based manner.

For instance, suppose ''w'' holds your instance of ComplexMatris in which you have
''set_num_synapse_states(3)''. This makes it a connectivity matrix which reserves
three state variables of type AurynWeight per synaptic connection. 
Now, decaying all elements of, say, state 3 by a factor ''foo'' is as simple as
''w->get_state_vector(2)->scale(foo)''.  
Adding two of the states for all synapses
becomes 
<code>
w->get_state_vector(2)->add(w->get_state_vector(3))
</code>

As you imagine these expressions can quickly become rather lengthy. 
It is therefore nice to declare shortcuts in your plastic Connection class such as: 
<code>
AurynSynStateVector * w_val        = w->get_state_vector(0); 
AurynSynStateVector * tagging_val  = w->get_state_vector(1); 
AurynSynStateVector * scaffold_val = w->get_state_vector(2);
</code>

You can now work with these as you are used with AurynVector or
AurynStateVector instances ''w_val->saxpy(foo,tagging_val)''