Fix page search index
Fix page search index

This change fixes some troubles in the search index:
- converts &nbsp; to spaces
- converts some others html entities to text
MichaelMaar/concrete5,MichaelMaar/concrete5,MichaelMaar/concrete5,avdevs/concrete5,TimDix/concrete5,matt9mg/concrete5,TimDix/concrete5,avdevs/concrete5,matt9mg/concrete5,avdevs/concrete5,TimDix/concrete5,matt9mg/concrete5