Release 4.0-alpha7

A few changes:

• make BES work with typechecking
• make read_phase_file and read_phase2_file into IO actions for BES.
• allow specifying model arguments as just -m Model arg1 arg2 instead of -m Model.hs ... --- arg1 arg2.
• use std::filesystem for file operations.
• target OS X 10.15
• alignment-consensus and alignment-gild can take a list of alignment files