Bugfixes for error handling and BoostFunctions

• Protect against exceptions while indexing
  Currently the cronjob indexing process will stop if an exception occurs
  while fetching metadata. This is now caught and the process can continue.

• Fixed bug with boosting fields
  When using the BoostFunctions parameter the wrong query/field
  gets overwritten. When the boost field is decoded it
  stored using numerical keys instead of the basename.
  This key (which is now numerical) is then later used by a call to
  array_search which forces all values in the array to be converted
  to a numerical value before comparing