1024-bit rsa keys,  Darwin,  expiration_days

generate 1024-bit rsa keys,  
do not treat Darwin specially in this respect, as openssl is there anyway, 
decrease expiration_days to an acceptable period.
catch conversion errors when updating settings
use '' as default value for form.get()
Merge pull request #142 from rmartinjak/issue141

fix #141 and catch conversion errors when updating settings
Merge pull request #118 from dimpase/patch-2

1024-bit rsa keys,  Darwin,  expiration_days
Version bump to 0.10.5