Support UTF-8 and scroll longer labels on the screen

[sabeechen]

This PR:

• Makes the E-TKT UTF-8 aware by parsing string contents to determine character position, length, etc
• Uses the UTF-8 awareness to avoid substituting placeholder characters for the special characters it supports.
• Makes the E-TKT scroll longer labels as its printing.
• Renders special characters (♡, ☆, ♪, €) by picking and choosing different characters from different fonts for the best readability on the low-res screen. Small rant: this was exactly as tedious as it sounds, but I think I did the best with what was available in U8g2lib.

Reviewer notes:

• I would have normally to split this into two PR's, but the logic for rendering characters of different widths is pretty intermingled with the logic for scrolling the display, so I just made it all one.
• The auto formatting seems to want to put the big charSet map one line, which seems ugly to me but I didn't want to fight the formatter.

Since the website doesn't support printing labels long enough to trigger the screen scrolling (yet!) you can send labels using the command line, for example:
Linux (bash)

curl -vvv -X POST http://192.168.0.145/api/task -H 'Content-Type: application/json' -d '{"parameter":"tag", value:" This♡label☆is♪too€long@to$fit "}'

Windows (powershell)

$data = @{'parameter'='tag';
          'value'=' This♡label☆is♪too€long@to$fit '
}
Invoke-WebRequest -Uri http://192.168.0.145/api/task -Method POST -Body ($data|ConvertTo-Json) -ContentType "application/json"

[andreisperid]

Great work @sabeechen 😀

I've just tested it here and just had a minor issue (invalid conversion from 'char' to 'const char*' [-fpermissive]), but fixed in 3c09061, check it out if it makes sense.

[sabeechen]

That edit looks good, thank you. The E-TKT I do development on (I have two now!) is in rough shape hardware-wise and I have to make a bunch of kludgy code edits to keep it calibrated, which I then have to revert before I make a PR. I'll be more careful about it in the future.

[andreisperid]

Absolutely no problem :)