cacheISOClasses allows to cache the list of
geometa classes or extended. This is especially required to fasten
the decoding of metadata elements from an XML file. It is called internally
by geometa the first function getISOClasses is called
and each time the function readISO19139 function is called to
integrate eventually new classes added by user to extend geometa model
(case of ISO profiles).
cacheISOClasses()
cacheISOClasses()