This is the last PR, with submodules instead of subtrees, and a few more things:
add Catch2 dependency to the README
partial build options
correct debug flags on all platforms
when scons -c is called, print a note about deleting .sconsign.dblite (this addresses #330, which I still can't reliably fix, but deleting the file manually works every time)
This is the last PR, with submodules instead of subtrees, and a few more things: