Minor feature upgrade and bugfix

New features:

• draw grid in display
• grid-lines can be disabled in graph "settings and ranges" dialog
• line colors can be selected in graph "settings and ranges" dialog

Bug fix:

• The graph "settings and ranges" dialog could mishandle range entries depending on the system locale. Now the system locale is used for entry and display of ranges.

As usual, installation files for 64bit Windows (.msi), Linux Debian (.deb) and macOS (DragN'Drop installer; .dmg) are provided. For Linux, to avoid problems with library dependencies, a flatpak is available here: https://flathub.org/apps/details/de.halaszovich.PMbrowser

Full Changelog: v2.2.2...v2.2.3