list location code (net.sta.loc) in waveform fits plot

[carltape]

Station location codes can be important, especially for data sets using GSN stations, which have multiple sensors and location codes. It would be good to ensure that location codes are tracked and also displayed on the waveform fits plot and wherever else the station label is used. Many location codes will be blank; if they're not blank, they're often 00 or 10. Not urgent.

[rmodrak]

Is this the desired behavior in lines 18-21?

mtuq/mtuq/graphics/annotations.py

Line 18 in 5ff1a72

if len(station.location) > 1:

[rmodrak]

Added in #224