RFR [9] 8074716: IntelliJ IDEA project support

[Chris Hegarty]

A while back Maurizio announced a beta version of IntelliJ IDEA project
support for OpenJDK [1]. We got some great feedback and have made
several improvements since then. We believe that it is now suitable for
integration into the mainline JDK 9 forests. To that end, please review
the following changes:

  http://cr.openjdk.java.net/~chegar/idea/

Summary:

  - To create a new project run 'bash common/bin/idea.sh [MODULE-NAME ]+'
  ( a configuration must exist, as the script leverages its state )
  This creates a project in the .idea directory of top-level repository.
  An optional, space separated, list of modules can be provided, in
  which case the project will contain sources for only the given modules.
  Otherwise, the project will contain the sources for all JDK modules.
  The project can be opened by pointing IntelliJ at the top-level
  directory.

  - A project generation script is necessary, to include platform
  specific code, and code generated into platform / spec specific
  locations. It is not practicable to create a static standard project.

Further details on building and running tests were included in
Maurizio's initial mail [1], so I won't repeat them here.

-Chris.

[1] http://mail.openjdk.java.net/pipermail/discuss/2015-January/003645.html