Slicer perspective in "Sending data to..."

[astellhorn]

Is your feature request related to a problem? Please describe.

Its related to issue #2077, #1191, #1181.
--> In this branch I have started implementing the slicer perspective to the "sending data to..:" in the data explorer window.
--> During the code camp, we have discussed about if this major change is an improvement or too much of a change.
--> I have started this due to the future outlook of a more intuitive batch slicing and directly implementing this possibility after loading the data for e.g. the handling of rocking curves for magnetic SANS.
--> However, I will first try now to use the batch slicing option inside the current slicer of 2D plots and see if those major changes suggested above are needed: #2619

Reasons against moving the slicer option:

• it is a major change
• if it goes into "send data to..." it does not really fit to the current options of "Corfunc", "Fitting", etc.

Reasons for moving the slicer option:

• see issues Batch Slicer requires plotting of all 2D data sets to use in batch (Trac #1140) #1181 and Make Slicer Parameters box non-modal and add it to the Tools menu (Trac #1150) #1191 for handling of bigger data sets to batch slice
• if "Send data to..." or "Tools" is not the right place, see alternative idea below

Alternative idea:

• when new "data trend handling" (Jeffs idea presented during the code camp) is implemented, the plot option could be changed (or as new option) to display all selected plots of one trend in a combined window as in the image below...
• then in there if opening the slicers it would make sense that "slicer" handles just one of them, but "batch slicer" automatically all of them in one window (of one trend)
• in the batch slicer open the possibility to "plot single" or "plot together", and opening the possibility to automatically refer to the chosen trend variable for plotting e.g. the box sum as function of all temperatures, or all rocking angles, etc.: