Adds support for selection of LaTeX compiler

This commit adds support for selection of LaTeX compiler,
between LaTeX, pdfLaTeX, and XeLaTeX. It should be relatively
trivial to add more compilers. Additionally a small bug is fixed
wherein a LaTeX project has multiple subdirectories where
data is stored (e.g., /images/, /chapters/) and those directories
must be created in the temporary compilation directory for compilation
to succeed.