Use of jOOQ: Improve the code to COUNT a sub-select.

Use of jOOQ: Improve the code to COUNT a sub-select.

* src/main/java/org/glom/web/server/SqlUtils.java:
Move initial query creation into
build_sql_select_step_with_where_clause().
build_sql_select_count_rows(): Use the jOOQ API instead of
concatentating text, because a jOOQ Select*Step is a TableLike,
which is what from() takes.