Not part of a specific issue, but this change is a further attempt to make
TextArea and TextPane more compatible (i.e., useful as drop-in replacements)
for text-only processing.

Specifically, this change basically converts the existing "insert" and "delete"
methods in TextPane into "insertText" and "removeText" interfaces, which mimic
what is in TextArea, while leaving "insert" and "delete" there to call the
new methods.


git-svn-id: https://svn.apache.org/repos/asf/pivot/trunk@1603530 13f79535-47bb-0310-9956-ffa450edef68