Update GDSL definition for realms plugin

[sluongng]

Fix: #292

Problem:

• under realms, there is a "user-defined" closure and inside this closure is "authenticate" and "userExists". Reference: https://www.jfrog.com/confluence/display/RTF/User+Plugins#UserPlugins-Realms
• lack of "groups" and "user" property definitions under "authenticate" closure
• gdsl is hard to read and maintain

Fix:

• Reformat gdsl to a more human readable style
• add groups and user properties under authenticate closure
• add an annonymous method(no name) definition under realms

This fix should make current gdsl compatible with latest IntelliJ when run against some of the realms example plugin within this repo

[sluongng]

@jfrog-aparicio do you know how could i get a review and merge for this PR?

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