Update unoconv submodule

Bringing the very latest in updates from upstream, with our own added flavour.

This https://github.com/dagwieers/unoconv/commit/7573e8e655ddded65d3e4e4109728b6dad98e5c4 changes unoconv's behaviour as to where it places output files. Now it appears to default to placing them inside a directory that goes by the name of the output file you provide. Whatever. Rough fix to eyeVisor included.
Amend eyeDocs to take into account recent change in unoconv
Merge in updates to unoconv submodule
Amend working directory concept to take into account unoconv changes
Change focus of file existence test post-conversion

* Following from my comments in pull-request 30:
   - When unoconv is called, it creates the folder the output will appear within (if it needs creating)
   - It then tells [open|libre]office to convert the file
* This means that there's a chance that should the conversion fail, the folder will exist, but the converted file will not.
* The following alters eyeConvertor to check for the existance of the newly-converted file, rather than its enclosing folder