Fix path with spaces issue with "sp list-fonts"

fixes #22
Version bump 1.6.8
Merge branch 'hotfix_v1.6' into develop_v1.7

Fix path with spaces issue with "sp list-fonts"
Safety net: don't allow numbers in SetGrid

... otherwise bad things might happen.
Bugfix when searching through directories

When attr is not define, we shouldn't ask for details. I am not sure
why attr is not defined in some cases (symlinks for example?).


Closes #23
Merge branch 'hotfix_v1.6' into develop_v1.7

Bugfix when searching through directories
Add command line options 'profile'

Internal use only. This allows me to easily find out where the
bottlenecks are.