LDAP Refactor

[rodrigok]

• Mask LDAP_Domain_Search_Password; Closes Update LDAP Settings page to make it clearer for users - Also mask BIND Password from view and logs. #737
• LDAP without Bind or DN results in login with any information provided; Closes LDAP without Bind or DN results in login with any information provided #1437
• Add option to use more than one LDAP_Domain_Search_User_ID; Closes LDAP auth works with username but not with e-mail #1823
• Do not allow username changes for accounts from LDAP; Closes LDAP default username #1982; Closes Changing of username of a LDAP-user #2029
• Verify if slugfy is necessary; Closes LDAP default username #1982
• Sync ldap password; Closes For accounts auto-provisioned from LDAP, the user cannot set initial fallback password #1984
• Import user's avatar jpegPhoto; Closes jpegPhoto LDAP Integration #2042
• Add button to test configuration after save; Closes LDAP settings should be verified before saving -> locked out due to misconfiguration #1908

Closes #1395
Closes #1967
Closes #2146

TODO

• Option to define LDAP groups that create admin users; Admins from LDAP group #1196
• ldap aliases not being followed; ldap aliases not being followed #890

[engelgabriel]

LGTM