Remove phstore flag from style and replace ist by a generic hstore flag

Remove phstore flag from style and replace ist by a generic hstore flag
The generic flag is also usable for points and lines rather than only polygons.

This is useful in conjunction with the --hstore-match-only option
No! The test for FLAG_HSTORE is sufficient (FLAG_HSTORE is 16 FLAG_PHSTORE is 17) as we do bitwise and in comparison. I left the old flag-name for compatibility reasons only. FLAG_PHSTORE is the same as FLAG_HSTORE and FLAG_POLYGON