libmm-glib,common-helpers: allow yes/no as booleans in string

E.g. so that the settings passed on Simple.Connect() or
Bearer.Connect() are parsed correctly from the user string:

  daemon.notice netifd: wan (30476): simple connect=apn=internet,ip-type=ipv4,allow-roaming=yes
  daemon.notice netifd: wan (30476): Error parsing connect string:
  'Invalid properties string, unexpected key 'allow-roaming''

This also goes inline with e.g. the --create-bearer help in the man
page that suggests using yes/no for the allow-roaming setting.

(cherry picked from commit 15e8a78a15e458efae781d4905134e07043aad25)
1 file changed