Create warning message about limits

code (python) for checking:
```
from beakerx import *
xs = [];
ys = [];
for i in range(55000):
xs.append(i);
ys.append(i);

plot = Plot()
plot.add(Line(x=xs, y=ys))
```
We have limits = 10000 of objects for Plots without any warning message.

We needs create warning message about limits of data, like we done for another widgets: