Don't read and write from a file at once.

I think this is the cause for some errors with configs.
Fix bug in check_installed_packages.

`nil` is falsy.
Update toolbar's package descriptor.
Delegate PackageAttrs instance methods to the class.
Add a package for Hyperedit.
Update the package for Toolbar.
Add packages for RCS Build Aid and Science Alert.
Merge remote-tracking branch 'origin/master'
Add a package for PreciseNode.