This CL changes:
1. add function bitmap_to_string and bitmap_from_string, which will
convert a bitmap to/from string which contains all bit in bitmap
2. add function murmur_hash3_32, which will compute murmur hash for
input strings
3. make the function cast float to string the same with user result
logic
This CL make bitmap_count, bitmap_union, and bitmap_union_count accept any expression whose return type is bitmap as input so that we can support flexible bitmap expression such as bitmap_count(bitmap_and(to_bitmap(1), to_bitmap(2))).
This CL also create separate documentation for each bitmap UDF to conform with other functions.
