Fix patient descriptions to 'definition, status' if possible
Fixes handling of filters in the query cache

Previously, this code was adding a 'filter' attribute to the query.
The query_cache actually has a property called 'filters'.
Additionally, this now merges in the filters to allow for properties
such as 'filters.provider_id'.
removes empty hqmf precondition... this can happen in HQMF using the datediff operator
Merge pull request #114 from jtferns/patient_export_description

Fix patient descriptions to 'definition, status'
Merge pull request #118 from projectcypress/remove_empty_hqmf_precondition

removes empty hqmf precondition... this can happen in HQMF using the dat...
Merge pull request #117 from projectcypress/fix_query_cache_filter

Fixes handling of filters in the query cache
add cms and nqf ids to Measure.categories
continuous variable
Merge pull request #120 from yoon/cms_and_nqf_ids

Add cms id, nqf id, and continuous variable to Measure.categories