New Feature: import a path list to a units/includes (-Fu/-Fi) from text-file

Added a Button "Import Paths" to PathEditorDialog
Clicking on it, shows an OpenFileDialog to select a text-file to Import.
Importing is processed by TStringList.LoadFromFile();

The patch is usable on 1.2 and 1.3 Lazarus.

http://bugs.freepascal.org/view.php?id=25903