CObs format added and complex Corr print improved.

[fjosw]

I worked a bit on the string conversion of complex observables and correlators.

• CObs now have a __format__ method which allows for f-string formatting like this:

print(f"{my_cobs:+3}")
> (+0.018(465)+0.443(393)j)

• I use this to also improve the print output of complex correlators which now produces the following:

Corr T=4 N=1
x0/a	Corr(x0/a)
------------------
0	(+0.02(46)+0.44(39)j)
1	(+0.00(59)+0.43(37)j)
2	(+0.01(58)+0.64(47)j)
3	(-0.03(62)+0.45(51)j)

Please have a look @JanNeuendorf

PS: There is still no proper print output for matrix correlators.

[s-kuberski]

Looks good!