Support substring comparisons on list elements

[merkys]

While discussing #368 with @JPBergsma I noticed that comparisons on list properties having string elements can only use numeric comparison operators. This means, for example, that the following query is not allowed even on filter language grammar level:

species_at_sites HAS STARTS WITH "Si"

Since as of v1.1.0 there are not much of list properties with string elements, the issue is minor. However, such properties may arise in the future, thus I propose extending the grammar to allow such constructs.

Fix seems rather simple: replace

ValueList = [ Operator ], Value, { Comma, [ Operator ], Value } ;

with

ValueList = ( [ Operator ], Value | FuzzyStringOpRhs ), { Comma, ( [ Operator ], Value | FuzzyStringOpRhs ) } ;

(Similarly adjust ValueZip and SetOpRhs as well). I have not tried this for real, thus have not checked for grammar conflicts.

Pinging people usually involved in developing the filter language: @sauliusg, @rartino and @fekad.

[merkys]

@giovannipizzi and @gmrigna has encountered this recently while investigating means to implement biomolecule support (#389).