Merge branch 'master' of github.com:johanmattssonm/birdfont

Merge branch 'master' of github.com:johanmattssonm/birdfont

Substitutions for space character

White space fixes

Solve the backtrack issue

Skip empty ligatures in kerning display

Fix backtrack sequence for contextual ligatures
Generate contextual substitutions compatible with the currents version of
Harfbuzz.

Merge branch 'master' of github.com:johanmattssonm/birdfont

Fix OTF lookups

Restructure lookups in gsub table
This commit does also change the order of subtables in the gsub table.
1. Chained substitutions
2. Context for chained substitutions
3. Regular ligatures

Fix contextual ligature substitution

Merge branch 'master' of https://github.com/johanmattssonm/birdfont into HEAD

Process contextual ligatures in kerning and spacing tabs

Fix compilers warnings

Rename ligature collections

Contextual ligatures

Multiple subtables of contextual ligatures

Write the context for contextual substitutions (ligatures)

Add contextual ligatures to the GUI and fix directory privileges