Allow username to take no argument to erase value Once a username has been set, it could not be removed via the UI. Now, if no argument is passed to username, the value stored is replaced with NULL.

# use glob syntax.
syntax: glob

*~
*.py?
.*.swp
.swp
doc/build
build
debian/vmm
debian/*.log
debian/*.debhelper
debian/files
debian/*substvars
.pc