Allow setting LDAP values at proposal-create time

Settings aren't required and usually expected to be set in "raw" mode.
Exposing those to the UI would be overkill and rarely needed. However,
this is still better than only support setting them via chef/knife.
Merge pull request #110 from saschpe/release/pebbles/master-ldap-proposal

https://github.com/crowbar/barclamp-keystone/pull/110

Merged by devtool for cloudsleuth