Routine Name:	exists

Description:	Tests for existence of specified element or field.

Usage:		exists-flag = {exists element [field]}

		exists-flag	returned as 1 if element (or element field)
				exists; returned as 0 otherwise

		element		name or full pathname of element to test

		field		element field to test existence of
				(does not check whether field is nonempty)

Example:	if ({exists /cell/dendrite})
			delete /cell/dendrite
		end

		genesis > create compartment soma
		genesis > echo {exists soma}
		1
		genesis > echo {exists bogus}
		0
		genesis > echo {exists soma len}
		1
		genesis > echo {exists soma bogusfield}
		0

Notes:		

