Update readme.txt

updated to answer questions about ISO support for this customization (answer = "Yes!").
Update readme.txt

included note about gpt.properties settings for default DCAT JSON response
cached JSON file changes for 1.2.2

changes to support cached JSON file
Merge branch 'master' of https://github.com/Esri/geoportal-server
updated to include instructions for scheduled cached JSON file

updated to include instructions for scheduled cached JSON file
update download language
Merge remote-tracking branch 'upstream/master'