Add developer info + sample config about how to work with a RAM disk

Add developer info + sample config about how to work with a RAM disk

There are two files:
  - docs/developer/ram-disk/maven.config
  - docs/developer/ram-disk/settings-ramdisk.xml

The latter contains info about how to set up a development environment
inside a RAM disk. Both files are to be copied to the project's '.mvn'
folder in the root directory and adjusted according to the description.

Just in case, .gitignore ignores the files if they exist in '.mvn', so
they are not being staged and committed accidentally.

An additional screenshot shows how to configure the Windows Recycle Bin
to immediately delete files in order too save space on the RAM disk.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>