omit filename extension as in the rest of the file
feta accidentals: split into several files
font: rename draw_staff to draw_staff_if_debugging

Previous name was confusing: the stafflines are actually
not drawn unless 'test' is set to non-zero value.
font: clean up staffline-display in testing mode

Previous testing code was a mix of hideous copy&paste with
non-obvious passing glyph outlines around, which attempted
to produce additional glyphs in testing mode, so that there
would be both on-staffline and on-staffspace variations.

That code was completely unreadable and unmaintainable.

Instead i've introduced a global variable that determines
how the stafflines will be printed relative to the glyphs.
To see alternative configuration, just change that value.
remove feta-test-generic.mf and other testing files

they were just polluting the code
rename feta-generic to feta-other-generic; similarly parmesan-generic

these files are not for the whole font,
but just some glyphs that aren't in their own subfonts
rename feta-alphabet to feta-alphabet-generic

to conform to the convention
move brace-drawing procedure to separate file (and rename files)
factor out autometric_parameter declarations
factor out common inclusions and initializations
make comments more uniform
remove spurious else
include subfonts unconditionally
unify formatting and indentation