docker: add bcmath/ldap to Quibble images
The GoogleAppEngine MediaWiki extension indirectly depends on bcmath to
be available. It is built in HHVM but is not installed for php5.5 and
php 7.0. T196346
Some OpenStackManager tests trigger code in LdapAuthentication which
require the ldap extension T198336. It is built in HHVM but missing from
the php7.0 image.
Add relevant packages where they are needed.