* maintenance -- gradle

[dkimitsa]

• closed #701
• removed unused license parameter
• suppressed "warning: no comment" when building gradle plugin
• updated README.md
• displaying info message "Checking for RoboVM SDK (downloading if required)..." as getting SDK files from maven could take a while first time
• introduced RoboVMGradleException that aggregates error messages from cause exceptions, allows to have more detailed output:

• What went wrong: Execution failed for task ':launchIPhoneSimulator'.

  Failed to launch simulator Failed to read project RoboVM config file in /Users/dkimitsa/IdeaProjects/empty4del2 ParseError at [row,col]:[17,7] Message: The element type "frameworks" must be terminated by the matching end-tag "".

  instead of

• What went wrong: Execution failed for task ':launchIPhoneSimulator'.

  Failed to launch simulator