first steps to ly becoming a standalone module and tool
make ly separately packageable and installable
mention ly in INSTALL
touchup python-ly README
a ly command in the root folder that can be run without installing ly or frescobaldi

this is added just to test. It also works when Frescobaldi is installed.
ly command line interface

todo: parse the command itself
more command infrastructure
no error checking in Options.set_variable; do it while parsing
docstring
keep commands and files out of Options
add basic command performing
error handling on opening files
add language subcommand
main() function
handle - as stdin
add modified attribute to ly.document.Document
add option to print filename along with info; defaults to true when there is more than 1 file
doc
start with a fresh Options instance for every file
implement indent and reformat commands