add a buton in tracking to autoamtically create a in-memory tracking layer

[Remi-C]

This is a pure enhancement,
for futur realease.

The idea is that starting from 2.8, it is possible to create in memory vector layer.
Now it could be very useful to propose to the user to directly create a tracking layer with correct user_id and w_time, so it would be a one click operation to start tracking in a mono-user mode.

[yoyonel]

And propose at the end (of the session) where to save this layer in-memory (shapefile, push in db, etc, ...). Can be nice indeed ^^
(ps: i think it's not really difficult to add this feature)

[Remi-C]

Thanks for the correct labels and milestone.
Indeed saving it at the end is a good idea !
Maybe in few month this will give us ideas of enhancement.
Right now this is not hte priority ^^