[#2200] Add Executor.fetchCount(Select<?>) and Select.fetchCount() to
replace the projection by a COUNT(*) query

Conflicts:
	jOOQ/src/main/java/org/jooq/impl/AbstractSelect.java
	jOOQ/src/main/java/org/jooq/impl/Executor.java
	jOOQ/src/main/java/org/jooq/impl/SelectImpl.java