Extracted ModelEditor and Prototype builder into separate plugins that can be loaded and unloaded
The rendering of source files and widgets are now removed from projectManager and deferred to the corresponding plugins when project changes
Merge commit '3b980343874b88e70308b9fda29fbb3c947533b1' into sourcecode-editor-plugin

* commit '3b980343874b88e70308b9fda29fbb3c947533b1':
  fix for issue #145 + minor code cleanup
  additional fix for bug #141 (svg size not updated - merge from master)
  additional edits for removing function Save All Files; function Save Selected File is now always enabled (useful for handling situations where a file is edited using an external editor and the user wants to re-save the file shown in the model editor)
  removed button Save All Files, because users may get confused about the difference wrt Save Project
  fix for issue #144 (continued)
  fix for issue #144

Conflicts:
	src/client/app/plugins/prototypebuilder/interface.js
Merge commit '7b07b1f140c6ab73d699df15998e7b9e4dfcc635' into sourcecode-editor-plugin

* commit '7b07b1f140c6ab73d699df15998e7b9e4dfcc635':
  introduced additional feedback for projects with missing image file / missing main file (partially addresses concerns highlighted in issue #98)
  fix to mitigate issue #98
  patch that mitigates issue #121
  minor fix for widgets list (all widgets were erroneously highlighted as selected when opening a project)
  minor changes to improve feedback given with notification messages
  fix for issue #142
  additional fix for issue #145
  fix for issue #146 + minor code cleanup

Conflicts:
	src/client/app/plugins/prototypebuilder/interface.js
	moved builder/simulator view switching code to prototype builder plugin
Addresses issue #149
changes to widget labels are now updated in the widget list view
interface.js code cleanup
fixed failing testcases
Removed getFolderStructure from server and removed explicit folderStructure usage in client parameters - rendering files list now obtains folder structure from project based on the list of current project files
Restricted files retrieved from project folders using filters based on extensions
Updated  web socket messages to contain timing information for processing commands
PluginManager fires PluginEnabled and PluginDisabled events