Proposition to have all systems data as default for all TS related requests

@osauter Currently if you ask for ne, te or nete_rho you only get the main system even in the shot range where the edge system was available. I would like that the default be that you get data from all available systems.

The main question remains how to specify the different options. One possibility is:

Value of edge option	system
0	M
1	E
2 (Default)	M+E

Or we could introduce a main option, and both main and edge would default to 1.

I can take care of the implementation, once we agree.