bug 418091: synchronize document when Vex gets activated or deactivated

With this change, Vex should integrate better with the Eclipse
ecosystem. VexEditor does not operate on the input directly, but uses a
document provider as an intermediate (as all other Eclipse editors also
do). The integration is not perfect. Vex still uses it's internal
GapContent that is not synchronized with the document provider. This
results in two problems:
    The caret position gets lost when switching editors
    The undo history gets lost when switching editors

Change-Id: Idac0ff8022a6477fc99594f482cfd28f37f86e85
Signed-off-by: Carsten Hiesserich <carsten.hie@gmail.com>
diff --git a/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/messages.properties b/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/messages.properties
index 8571c4e..8bcd3a9 100644
--- a/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/messages.properties
+++ b/org.eclipse.vex.ui/src/org/eclipse/vex/ui/internal/messages.properties
@@ -71,16 +71,24 @@
 VexEditor.unexpectedError=Unexpected error opening {0}. Please report a bug at https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Mylyn%20Docs%20Vex
 VexEditor.loading=Loading...
 VexEditor.errorSavingStylePreference=Error saving style preference
-VexEditor.docChanged.title=Document Changed
-VexEditor.docChanged.message=The file {0} has been changed from outside Vex. Would you like to discard your changes or overwrite the external changes?
+VexEditor.docChanged.title=File Changed
+VexEditor.docChanged.message=The file ''{0}'' has been changed on the file system. Do you want to replace the editor contents with these changes?
 VexEditor.docChanged.discard=Discard My Changes
 VexEditor.docChanged.overwrite=Overwrite Other Changes
 VexEditor.docDeleted.title=Document Deleted
+VexEditor.docDeleted.canNotSave.title=Cannot Save
+VexEditor.docDeleted.canNotSave.message=The file has been deleted or is not accessible.
 VexEditor.docDeleted.message=The file {0} has been deleted from the workspace. Would you like to discard your changes or save to a new document?
 VexEditor.docDeleted.discard=Discard
 VexEditor.docDeleted.save=Save
+VexEditor.saveAs.overwrite.title=Save As
+VexEditor.saveAs.overwrite.message={0} already exists. Do you want to replace it?
+VexEditor.saveAs.error.title=Problems During Save As...
+VexEditor.saveAs.error.message=Save could not be completed. {0}
+VexEditor.saveAs.deleted=The original file ''{0}'' has been deleted or is not accessible.
 VexEditor.noUrlForDoctype=No URL defined for doctype {0}
 VexEditor.noContent=The file ''{0}'' contains no XML content.
+VexEditor.noProvider=Unable to get a document provider for the given input.
 
 VexEditor.Path.ProcessingInstruction=Processing Instruction
 VexEditor.Path.Comment=Comment