set special parameter _offset to enforce setting offset on query. _offset overrides calculated offet for standard pagination etc

Conflicts:
	src/fhir/fhir_version.coffee

Author: karsiwek-kainos

src/fhir/query_string.coffee

@@ -92,6 +92,9 @@ specials =
   summary: (query, left, right)->
     query.summary = true
     query
+  offset: (query, left, right)->
+    query.offset = parseInt(right)
+    query
   id: (query, left, right)->
     ids = right.split(',').map((identifier)->
       i = identifier.trim()

src/fhir/search.litcoffee

@@ -229,6 +229,9 @@ To build search query we need to
         if expr.page != null
           hsql.offset = (expr.count || DEFAULT_RESOURCES_PER_PAGE) * expr.page
 
+        if expr.offset != null
+          hsql.offset = expr.offset
+
         if expr.joins
           hsql.join = lang.mapcat expr.joins, (x)->
             mk_join(plv8, alias, next_alias, x)