Simplifications for ToolPanelManager.get_shed_tool_conf_dict.

None of the components using this method are using the index any more - so eliminate it. Also introduce a new ToolBox method to hide the details of ToolBox.shed_tool_confs from this method.
Eliminate another directory access to ToolBox.shed_tool_confs.
More hiding ToolBox.shed_tool_confs (from shed_util_common.py).
More encapsulation of shed_tool_confs - this time from tool shed install models.
Abstract tool lineage handling out of ToolBox.

Start work on infrastructure to support tool lineages not defined within the tool shed install model.
Abstract out higher-level helpers in ToolBox for lineage reasoning.

Reduces code duplication slightly and simplifies __add_tool_to_tool_panel (cyclomatic complexity reduced from 20 to 14).
Improved unit testing support for unit tests.
Allow multiple tools with the same id in ToolBox.

How to use:

 1.) Place multiple tools with different IDs in your tool conf.
 2.) ... ummm ... no step 2 - just use the tools.

Implementation:

The Tool Shed allows tool lineages by assigning each tool version a GUID and tracking versions in a database. This
implementation works by simply allowing the ToolBox to contain multiple tools with the same ID and orders them by the version specified by the tool author.

To track enable this a second tool lineage has been introduced that just uses tool versions instead of a database (non-toolshed installed tools are not longer placed into the Tool Shed install database). The ToolBox has been updated to allow multiple versions per tool id (defaulting to the 'latest' version for all operations which do not specify a version).

Unit tests working through most of the ToolBox and tool panel have been added, as well as functional tests exercising the Tools API. Manual tests against the new tool form seem to demonstrate the tool switching and tool re-running work with only minor changes to the tools API and the job handler.
Introduce ToolPanel abtraction.

There are some repeated operations on an odict in Toolbox that could be cleaned up (fewer lines of code, more readable) with new abstraction in place. Starting with __add_tool_to_tool_panel but will work its way to other methods in Toolbox eventually.

Abstraction reduces cyclomatic complexity of Toolbox.__add_tool_to_tool_panel from 23 down to 18.
Move more logic into ToolSectionElements, raising level abstraction in Toolbox.
Replace another repeated idiom in Toolbox with higher level method in toolbox.panel.