Allow for SSID's containing a single quote

[Sibert]

SSID's are allowed to contain single quotes ('). This change allows the configurator to work with SSID's (and passphrases) to contain single quotes. Previous version causes following behavior:

SSID: It's a great network name
Pass: RatOSIsGreat

$ wpa_passphrase 'It's a great network name' 'RatOSIsGreat'

This won't work, so it should be

$ wpa_passphrase "It's a great network name" "RatOSIsGreat"

hence this change

[miklschmidt]

Thanks!

I think a better solution is to use spawn instead of exec, we don't need to quote or escape the arguments that way (but the process can be orphaned, although that seems like an OK tradeoff here).