careful not to overwrite manually set box sizes
tweaked the fake box dimensions
added a pxValue method to dimensions
careful about inheritting non-LaTeXML attributes to math nodes
use pxValue instead of ptValue for pixels; add missing \fi
updated tests for tweaked box sizing
added \tracingcommands; refactored conditionals to better modularize code and to better support tracing
adjustments to DefConditional to combine all conditionals, elses, etc
added tracingcommands support; refactored definitions of \else,\or,\fi and \ifcase
refactored \unless