Allow to autocomplete plate solver/focus with the last exposure

[albireox]

When using the plate solver and focus features in most cases we need to keep copying the path from the last image. We should add a button to add the path to the last image taken.

In the plate solver we should also be able to auto-complete the RA/Dec using the pointing of the telescope from the RA/Dec coordinates in the header of the last image or getting it from the SiTechExe server.

In the focus sweep section we should be able to auto-complete the current position of the focuser.