CDAP-556 Communication over SSL between AuthServer and LDAP

This allows the enabling of communication between the AuthServer and an LDAP instance over SSL. 

By default, certificate checking is enabled. You can override this property by setting ``ldapsVerifyCertificate`` in the configuration.

Docs will be updated separately.
The try block can be replaced by -
```
ldapSSLVerifyCertificate = configuration.getBoolean(authConfigBase.concat("ldapsVerifyCertificate"), true);
```