Syntax errors and Lubuntu support

I fixed unnecessary spaces in the ">&2" error redirection, because they tripped up my version of bash (4.3.11).
I also added support for Lubuntu, and tested it.
This will not work for other LXDE based distros, because of the specific path to the pcmanfm config files.
An automatic way to discover this path will be needed for a more generic solution.
From my tests, when using a single monitor there is no noticeable flicker,
and on two monitors the first one is changed immediately while the other takes a second.
All in all it works pretty well, and it's the only method I found to work on multiple monitors, at least until the linked bug is fixed in pcmanfm.