Allow negative integers

Usage of PROGMEM for bars and intToBars

- v1.0.4: DoubleBarPot.ino uses 8036 bytes and 498 bytes of RAM
- v1.0.5: DoubleBarPot.ino uses 7446 bytes and 310 bytes of RAM
- v1.1.0: DoubleBarPot.ino uses 7538 bytes and 230 bytes of RAM

Debug on LCDPROGRESSBAR_DEBUG usage

Storage and RAM gains:
> v1.0.4: DoubleBarPot.ino uses 8036 bytes and 498 bytes of RAM
> v1.0.5: DoubleBarPot.ino uses 7446 bytes and 310 bytes of RAM

Adding .project file to be ignored

Added support to display 1 bar only + example

Added example with trimmer potentiometers

Copyright year corrected

Initial release