Added logscale options

[OhadNir9]

No description provided.

[OhadNir9]

Graph of exponential function fit with y axis logscaled:

I managed to solve the axis format issue with FuncFormatter, but still not in scientific style (100000 instead of 10^5).

In second thought, maybe the problem is in toga, because the CLI produces good figures.

[saroad2]

Thank you @OhadNir9 for the contribution!

I didn't change a lot of things, just moved the scaling switches next to the axis titles text inputs, and added command shortcuts to toggle those switches (ctrl+x and xcrl+y).

I fixed the ticks problem using the FuncFormatter as you did in EddLabs/eddington#104. The reason for that bug is because of beeware/toga-chart#11. We have to wait until it is fixed in order to solve the problem here. Until then, at least we have something that works.

If you have the time and endurance to try and solve the problem in toga-chart, that would be awesome. I didn't get the chance to sit down and try to tackle this bug because of prior commitments.