[Concrete CMS Adapter] Search Express entries

[hissy]

Concrete CMS manual site has a glossary and FAQ database built with Express. However, the current candidate search service can't get information from Express entries. Let's add Express entities as a data source.

[broreece]

I'll look into this now

[broreece]

I made a PR: #2 @hissy however I'm not 100% confident on if the approach taken was the correct one for us. Please let me know if you feel I should change the approach I took!