RFR: 8279877: Document IDEA IDE setup in docs/ide.md

[Daniel Jelinski]

Currently the information about using IDEA can only be found on mailing lists.

Additionally fixed the documentation for Visual Studio; the target `ide-project` does not exist.

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Commit messages:
 - Update IDEA and VS documentation

Changes: https://git.openjdk.java.net/jdk/pull/7044/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7044&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279877
  Stats: 37 lines in 2 files changed: 31 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7044.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7044/head:pull/7044

PR: https://git.openjdk.java.net/jdk/pull/7044