RFR: JDK-8244093 Move all IDE support into coherent structure in make directory

[Magnus Ihse Bursie]

The IDE support in OpenJDK unfortunately leaves a lot to be desired. 
There have been a garden variety of attempt to support a specific IDE 
for a specific part of the code base, cluttered all over the code base.

This patch is a first attempt go get one ring, eh..., structure, to rule 
them all.

I have moved all IDE project creators into the following structure:

make/ide/<ide>/<part of the code>

where <part of the code> is one of currently "hotspot", "langtools" or 
"jdk", and <ide> is one of "vscode", "idea", "netbeans" or "vistualstudio".

This will not magically improve IDE support, but will at least make it 
clearer what we have and what we are missing.

Ownership of the IDE support is notoriously vague. I've cc:ed a bunch of 
people who has shown interest and/or submitted fixes to some of the IDE 
projects according to the hg history. I'd appreciate it if anyone who is 
interested in a particular case for IDE support can verify that it still 
works. I've tried my best to make sure all targets can run without 
errors, but I cannot verify that the IDE environment themselves are correct.

If you know about an IDE project that is no longer relevant, and should 
be removed instead of shuffled around, please let me know!

Bug: https://bugs.openjdk.java.net/browse/JDK-8244093
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8244093-move-ide-support/webrev.01

/Magnus