Added functions to remove elements from the end of a sequence

	modified:   container.ml
Added functions for partial substitution and splitting/generation of
unary terms

	modified:   term.ml
Factored out a 'term_table0.ml' from 'term_table.ml'

The core algorithm of the term tables has been factored out.

The user data is no longer stored within the term table. The table
represents the pure structure of the terms.

	modified:   term_table.ml
	modified:   term_table.mli
	renamed:    term_table.ml -> term_table0.ml
	new file:   term_table0.mli