Enable LDAP PHP extension in all versions

[leoneparise]

We think that most organizations have LDAP installed and should be enabled by default.

Fixes #24

[pierreozoux]

@tianon @yosifkit what do you think?

I know the official images should stay small, but ldap is actually a broadly used feature.

Let's deal with this PR :)

[tianon]

Hmm, isn't this related to docker-library/php#85? Any idea what --with-ldap-sasl adds/changes?

[tianon]

FWIW, I do think that enabling this makes sense here (especially given that it appears to be a core feature of ownCloud), but I'd like to make sure we figure out what makes SASL support special before we move further (especially since that might affect what we do here).

[ItalyPaleAle]

+1 for LDAP support in the Docker image

[ItalyPaleAle]

@tianon SASL is another authentication method for OpenLDAP, but I wouldn't say it's particularly important. See: http://www.netid.washington.edu/documentation/ldapauth.aspx
I believe most users will use the "Simple" authentication, for example with a dedicated service account.

[sebastiangraf]

+1 for LDAP support in the Docker image. Like @EgoAleSum stated, I think as well that basic authentication is sufficient at the moment and would be a huge benefit for people using this image.