Legend channelnames fix

[mikelovskij]

Just some minor fixes:

• Moved the wait time between one reconnection attempt and the other before the restart method, in order to use the re-created iterator just after its creation, since waiting between the creation of the object and the first iteration seems (especially if the wait is more than 30 second) to increase the possibility of failing to retrieve the data.
• If vmin and vmax are not set and the colormap of a spectrogram changes due to an autoscale during the plotting, now the colorbar changes accordingly.
• Solved a weird issue in the spectrum monitor: it happened that the first time the spectra were plotted, they were plotted in the wrong order, leading to wrong colors with respect to the ones set in the config file. After the first iteration, the spectra would have been replotted in the correct way, but the legend not, keeping the wrong colors. By changing the iterator from self.spectra to self.channels now the spectra are plotted in the correct order since the first iteration and the legend is created correctly.
• Added the suptitle (with the plotting time) to the timeseries monitor.