docs: add hack back in to avoid creating a python module package in API docs, switch to imgmath extension

sphinx-bindoc: add try/except loop in reading help messages from scripts to skip problematic scripts

docs Makefile: ignore gstlal_inspiral_add_dt_dphi_snr_ratio_pdfs and gstlal_inspiral_add_p_of_ifos_given_horizon autodocs

fixed side-scrolling issue in docs by having page-width set to percentage rather than fixed pixel width