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.
668951708f2f28f49da94479a89c40ab8c8a9b01 trunk
668951708f2f28f49da94479a89c40ab8c8a9b01 vmm-0.4
9b39f828aa8a7661582859ec75e1423c38dbbef2 vmm-0.3.1
bb0aa2102206cd25a99e64d0b94bcd6c2018d3df vmm-0.3
bc41dfcef0ad915ccca987b1b381d8c68ab70f2f vmm-0.5
dc98cc162c66d8a5227b6e7c5e7215757159688c vmm-0.5.1
3e972996da7f135f0a91afaea831befbac4c3351 vmm-0.5.2
668951708f2f28f49da94479a89c40ab8c8a9b01 trunk
0000000000000000000000000000000000000000 trunk