Implement timing (xslot) selections in searches

[gracemyz]

• if “ignore x-slots” is selected, then no x-slot information is shown in the module; the search target will operate in the absence of timing relations (e.g. if you want to search for any sign that has a circular movement anywhere in the sign)
• if “use an abstract x-slot” is selected, then a version of the module with 1 x-slot is opened; the search target will look for matches to the built x-slot, but the x-slot can occur anywhere in the sign (e.g. looking for any x-slot that has a head location at the beginning of the x-slot, regardless of whether that x-slot is x1, x2, x3, or whatever)
• if “use an abstract whole sign” is selected, then a version of the module with ‘whole sign’ and ‘beginning’ and ‘end’ timepoints is opened; the search target will look for matches for the elements associated to the whole sign, the beginning of the sign, or the end of the sign, ignoring anything in the middle (e.g. looking for any sign that ends with a signing space location, i.e., is at the endpoint of whatever the last x-slot in the actual sign is)
• if “use concrete x-slots” is selected, the user then also enters a specific number of x-slots, and a version of the module opens with that number of x-slots; searches will have to match exactly (e.g. looking for 2-x-slot signs that have a head location at the end of x1 and at the midpoint of x2)