Address property documentation concerns.

A context based property query that applies to all fetch operations and a local

property query.

Where both the context and local queries include a clause with the same name,

the local clause is used and the context one ignored.

For example, a context property query of "fips=yes" and a local property query

of "fips=no" would result in algorithms that have the "fips" property set t

"no".

the local clause overrides the context clause.

=head2 Override

It is possible for a local property query to override a clause in the context

It is possible for a local property query to remove a clause in the context

property query by preceeding the property name with a '-'.

For example, a conxtet property query that contains "fips=yes" would normally

For example, a context property query that contains "fips=yes" would normally

result in implementations that have "fips=yes".

However, if the setting of

the "fips" property is irrelevant to the operations being performed, the local

property query can include the clause "-fips".

However, if the setting of the "fips" property is irrelevant to the

operations being performed, the local property query can include the

clause "-fips".

Note that the local property query could not use "fips=no" because that would

disallow any implementations with "fips=yes" rather than not caring about the

setting.