Cache in GRADLE_HOME and cache JDKs by vendor

[hakanai]

Building on top of the Windows batch file PR, but adding:

• Updated the shell script patcher to also put the JDK into $HOME/.gradle to match the Windows one
• Added "vendor" property to distinguish two JDKs with the same version but different vendors, updated both scripts to use that

With this I think all the customisations we had done to our own wrappers are covered, but I do wonder whether a cleaner way to patch the files after this plugin patches them would be nice...