Java.txt: fix wrong method name in code example
Java.txt: remove trailing whitespace
Java.txt: add comment about PixelsType search

This block of code, which specifically locates the PixelsType
corresponding to that of the source image, is lengthy enough to
warrant a descriptive comment and whitespace separation.
Java.txt: fix indentation levels
Java.txt: add comment for image creation step
Java.txt: standardize comment style
Java.txt: standardize descriptive header
Java.txt: simplify plane data structure

The linearized map was a bit convoluted and rather outside the scope of
the example. A list works just fine here.
use warning box to warn of loss of users' data
Merge pull request #478 from ctrueden/fix-code-examples

Fix Java code examples
Merge pull request #484 from mtbc/warn-data-loss

put permissions warning into a proper warning box