Customization of character used in meters

[theking2]

The current fixed character | is quite hard to read, customization not possible. Allow the user to change the bar character in a block character like '█'

It could also be considered to use ░ ▒ ▓ or the following for more accurate metering:

Unicode	sign	name
2588	█	FULL BLOCK
2589	▉	LEFT SEVEN EIGHTHS BLOCK
258A	▊	LEFT THREE QUARTERS BLOCK
258B	▋	LEFT FIVE EIGHTHS BLOCK
258C	▌	LEFT HALF BLOCK
258D	▍	LEFT THREE EIGHTHS BLOCK
258E	▎	LEFT ONE QUARTER BLOCK
258F	▏	LEFT ONE EIGHTH BLOCK

(now how do I label this as a FR?, clicking on Labels has no effect)

[Explorer09]

Look like a duplicate of #647