nemo-view: Fix warnings produced (particularly by nemo-dropbox) when
non-unique extension menu items are added through the menu-building recursion
Fix home toolbar icon
Never allow an icon to be scaled less than 1px width or height (this is an issue
with icons that are 5px x 55 px for example that must be scaled to fit the current
view's zoom level.) - reproduced with android sdk.

Fixes #598
Merge pull request #599 from RavetcoFX/a10

Fix home toolbar icon
2.2.1