Print a notification at the beginning and at the end of the AC.
Add symbolic results interface

It is now possible to access the results from a symbolic simulation
through a dictionary-like interface.

Eg.

ttresults = r['symbolic'][0]
print "VU1o = %s", str(ttresults['VU1o'])

The dictionary is case insensitive.

The same dictionary also accepts sympy.Symbol instances, which can be
recovered from the results set calling the function as_symbol()

VU1o = ttresults.as_symbol('VU1o')
print "%s = %s"%(VU1o.name, str(ttresults[VU1o]))

An additional helper function is provided to get many symbols at once.

Eg.
s, E1, C1, R1, V1 = ttresults.as_symbols('s E1 C1 R1 V1')