RFR: 8267418: IntelliJ build and test of JavaFX does not work [v2]

[Marius Hanl]

> ~~Question: I was wondering, should I create a ticket for this as well? Given the fact that I don't have an https://bugs.openjdk.java.net account, I need to use the official bug reporting tool, which looked a bit overkill to me since someone needs to check my created ticket, while this PR is only affecting the IntelliJ IDE with OpenJFX and not the JavaFX platform directly.~~
> EDIT: Thank you, Kevin. :)
> 
> This PR fixes the errors you get when cloning and working with OpenJFX in IntelliJ IDE:
> - The **.idea/misc.xml** is modified to use **JDK_11** as language level instead of JDK_8. 
> For IntelliJ users: This is the language level shown inside the **Project Structure**. (File -> Project Structure...)
> - The **.idea/base.iml, .idea/controls.iml, .idea/fxml.iml, .idea/web.iml, .idea/graphics.iml** are modified to include/recognize JUnit 4. Also the shims are included/recognized (as test resource, this is very similar to the configuration inside the .classpath file from Eclipse)

Marius Hanl has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Using gradle for the project structure (Loaded Gradle build scripts in IntelliJ)
 - Merge remote-tracking branch 'openjfx/master' into intellij-ide-fixes
 - Made IntelliJ build working

-------------

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/506/files
  - new: https://git.openjdk.java.net/jfx/pull/506/files/aecc9e68..763e81e9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=506&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=506&range=00-01

  Stats: 1076 lines in 37 files changed: 746 ins; 168 del; 162 mod
  Patch: https://git.openjdk.java.net/jfx/pull/506.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/506/head:pull/506

PR: https://git.openjdk.java.net/jfx/pull/506