Support zone map for column

[imay]

we should support zone map for column include min/max value for column page. When scan data, we can use this information to eliminate data loading.

We should add a ZoneMapBuilder which will encode column zone map information into a page, and ZoneMapDecoder will decode zone map and be used to do some filter. some detail should be discussed later.

#1305

[kangpinghuang]

here is my design:

1. define ZoneMap with serialize and deserialize
   class ZoneMap {
   public:
   serialize();
   deserialize();
   private:
   std::string min_value;
   std::string max_value;
   // if the whole page is null
   // if true, omit min_value and max_value
   bool is_null_page;
   };

2. add ComparableEncoder to encode the value as comparable binary
   add a ComparableEncoder that can encode column value to comparable binary, and store them to ZoneMap.
   And then we can use binary to compare min/max value with predicate value directyly. do not have to care about the field type when filter the page

3. define ZoneMapBuilder
   class ZoneMapBuilder {
   Status add(ZoneMap zone_map);
   };
   add should call zone_map's serialize api and BinaryPlainPageBuilder to store the serialized zone map value.

4. define ZoneMapDecoder
   class ZoneMapDecoder {
   Status load_zone_map(ColumnZoneMap* column_zone_map);
   };
   load_zone_map use BinaryPlainPageDecoder to get the serialized zone map and the call ZoneMap.deserialize the get ZoneMap and the ColumnZoneMap.add(zone_map) to construct column zone map.

5. define ColumnZoneMap
   class ColumnZoneMap {
   Status add(ZoneMap page_zone_map);
   int compare_to_min(const std::string& value, int page_index);
   int compare_to_max(const std::string& value, int page_index);
   bool is_null_page(int page_index);
   private:
   int _page_size;
   // min value array
   std::string* _min_value;
   // max value array
   std::string* _max_value;
   bool* _is_null_pages;
   };