SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This replaces the glyph width spinbox in the font editor with a
checkbox when editing fixed width fonts that indicates if the
currently selected character's glyph is present in the edited font
(For variable width fonts a non zero width implies presence)
This commit also changes the background color of glyphs in the glyph
map based on the presence of each specific glyph in the font.
Fixes glyphs not updating when loading between fonts at the same
index. Fixes GlyphEditor spinbox inadvertently modifying width
of last selected index.
This makes it easier to work in FontEditor at low resolution.
Previously glyph map resized itself and the parent window to
accomodate fonts, which isn't ideal. Users typically control
window size/position after launch; widgets have to make do.
