Fix spacing of open delimiter from \left...\right.  Issue #889.
Allow \newenvironment to provide an optional argument.  Issue #881
Allow commas in place of decimals in TeX dimensions.  Resolves issue #856.
Combine multiple elements into a single typesetting pass.  Issue #873.
Merge branch 'issue889' into develop.  Issue #889.
Merge branch 'issue881' into develop.  Issue #881.
Merge branch 'issue856' into develop.  Issue #856.
Merge branch 'issue873' into develop.  Issue #873.