The commit adds a recursive parser for datatype expressions which allows nesting of validators,
this allows for complex expressions like "list(or(range(0,65535),'infinite'))" to allow a list of
values which are either integers between 0 and 65535 or the literal string "inifinite".
That change also deprecates combined datatypes like "ipaddr" ["or(ip4addr,ip6addr)"] or
"host" ["or(hostname,ip4addr,ip6addr)"]
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