Tons of work on ncreel (#627, #749, #694)
Improve reel demo: get input wired up once more, avoid the FPS demo at bottom, print pointer and line count in each tablet, use new ncreel API. Improve notcurses-ncreel explorer: kill memory leaks (#694), draw tablets better, use new ncreel API. Fix bug in ncreel core where cruft could be left on the screen, via a very gross brute force algorithm. I'll likely come back and make this a bit less ghastly in the future #749. Remove weird one-off input system from ncreel, residue from outcurses. Make some of the normalizing changes speced out in #627
* ncreel: give each tablet an index, and print it #749
* reel: eliminate FIXME + param to insert_tabler() #749
* ncreel: label tablets with their adress to correlate against debugging logs #749
* more terminal environment variable notes
* TERMS.md: add Sakura, st
* ncreel: move legend out of reel proper
* ncreel_options: dump min/max_supported_rows/cols #627
* ncreel: remove weird one-off input layer #627
* ncreel: add ncreel_offer_input()
* reel demo: call demo_getc()
* reel demo: rig up input to demo main
* ncreel: drop ncreel_del_focused(), properly bind tablets
* reel demo: don't free up necessary plane
* ncreel: don't pull absolute locations of tablets
* ncreel: place tablets correctly in boundrel
* reel demo: add back support for left/right
* reel demo: restore thread movement
* ncreel: remove a great deal of complexity
* reel demo: stay out of FPS graph's way
* ncreel: give each tablet an index, and print it #749
* reel: eliminate FIXME + param to insert_tabler() #749
* ncreel: label tablets with their adress to correlate against debugging logs #749
* ncreel: move legend out of reel proper
* ncreel_options: dump min/max_supported_rows/cols #627
* ncreel: remove weird one-off input layer #627
* ncreel: add ncreel_offer_input()
* reel demo: call demo_getc()
* reel demo: rig up input to demo main
* ncreel: drop ncreel_del_focused(), properly bind tablets
* reel demo: don't free up necessary plane
* ncreel: don't pull absolute locations of tablets
* ncreel: place tablets correctly in boundrel
* reel demo: add back support for left/right
* reel demo: restore thread movement
* ncreel: remove a great deal of complexity
* reel demo: stay out of FPS graph's way
* reel: tighten up reel following redraw
* reel: fix upper-left corner of topless perimeter
* ncreel: print linecount, return clipped value
* reel: draw focused tablet relative to reel
* reel: brute force decruftification, how embarrassing #749
