Add obs. and ensemble at initial time in 4D tests

[benjaminmenetrier]

Add obs. and ensemble at initial time in 4D tests.

[andreapiacentini]

Thank you Ben. I've approved the two other requests.
About this one we should probably ask Jérôme.
In the real AQ and monarch 4DEnsVar applications, the 24 hours runs use 25 subwindows including the first and last that are half the duration of the central ones.
The time handling in 4D LETKF is still hard to understand for me. I've given up my first try of tracking the GeoVals extraction and the time matching between States and UFO observers. Any hint (or name to ask to) ?