1. Updated "dynTextBox.Text" property to be read-only
2. Added new constructor "dynTextBox(string initialText)"
3. NodeModel classes that require initial text to display in "dynTextBox" will set it through the constructor
Merge branch 'master' into DynEditBox
1. Renamed "dynTextBox" to "DynamoTextBox" and "dynStringTextBox" to "StringTextBox".
2. Removed setter for "DynamoTextBox.Text" property.
3. Made "DynamoTextBox.Commit" method protected (so it is not accessible externally).
Implemented "DynamoTextBox.BindToProperty" method to explicity call "UpdateDataSource" without recording changes for undo. Also implemented "PreUpdateModel" to record a model-change for undo.
Merge branch 'master' into DynEditBox

Conflicts:
	src/DynamoCore/UI/UIPartials.cs
Re-introduce Undo/Redo menu items in DynamoView.xaml
Merge pull request #498 from Benglin/UndoMenuItems

Re-introduce Undo/Redo menu items in DynamoView.xaml
Merge branch 'master' into DynEditBox
Updated "StringInput.SetupCustomUIElements" method to use the new "BindToProperty" method
Merge pull request #499 from Benglin/DynEditBox

DynamoEditBox enhancement work
cleaned up TryGetElement code
bad logic fix in TryGetElement
incorrect workspace assigned for collapsed nodes

fixes #461
reordered code
fix for #435
free form could preserve element on re-evaluate with RevitAPI enhancement
Merge branch 'master' of github.com:ikeough/Dynamo
updated for changed TryGetElement call