update README file

README file needs to be reviewed for ARC6.0, todo list

Description

README file needs to be reviewed for ARC6.0, todo list

I suggest everyone puts their names near the items we need to fix and remove the entry once it is done.

• remove/update outdated information @all
• refresh list of dependencies @floridop @ellert @waananen @aleksandr.konstantinov @dcameron @maikenp @andrii
• add information about how to find packages for apt distros @floridop