[Veltools] revised ToolboxManager proposal

[Nathan Bubna <na...@esha.com>]

Ok Gabe,

Here's the code again.  Changes from my last proposal are:
-changed ContextTool to ViewTool (that's view as in "view layer" not
"velocity view servlet")
-synchronized instantiation of session tools in ServletToolboxManager

To summarize the proposal:
Add the seven attached classes:
ToolboxManager
XMLToolboxManager
ViewTool
ToolInfo
DataInfo
ViewToolInfo
ServletToolInfo

Remove the following classes:
ServletViewToolLogger
ContextViewTool
LogEnabledViewTool
LogEnabledViewToolImpl
ServletViewTool
ThreadSafeViewTool
ViewToolLogger

The following classes are changed by the attached patch:
ServletToolboxManager (also attached as a file)
ViewContext (javadoc change only)
MultiViewsTool (implement ViewTool)
ErrorsTool (implement ViewTool.  log to ServletContext directly)
FormTool (implement ViewTool)
LinkTool (implement ViewTool. log to ServletContext directly)
MessageTool (implement ViewTool. log to ServletContext directly)
DateTool
MathTool
ParameterParser
ToolLoader (refactor to return class instance instead of directly
manipulating context)

Nathan Bubna
nathan@esha.com