Cleaning up javascript directory.

Moved external library files into lib subdirectory.

Changed script tags in all example apps to refer to moved files.

Removed vgd3 related files, including stats app.

Removed barchart.js and id.js - not necessary going forward.

Removed a reference to datatwiddle.js in CMakeLists file.
Renamed top-level "lib" directory to "js", and updated all example applications.
Renamed local copy of vega.js with version number.
Added a fun "default" index page.
Converted tangelo.util.svgColorLegend into jquery plugin and adapted all client applications to make use of it.
Converted landingPage function into jquery plugin, and updated examples index driver.
Converted control panel core function into jquery plugin.
Converted navbar core function into a jquery plugin.
Can now specify config callbacks either in div data attributes, or as arguments to plugin function.
Removing obsolete code.
Improved "defaults" code, moved to util.js, made all apps correct with respect to defaults function.
Severely simplified defaults code - now simply returns an object containing the default config options; changed client code to match new interface.
Removing census.py service.
Removing mention of census.py from CMakeLists.txt
Moved drawer_toggle() and drawer_size() functions to controlPanel.js
Simplifed drawer toggle code, renamed function with camelCase.
Moved test services into test subdirectory
Making installation of mongo and impala services optional.
Dropped submodules (except for date, since it has generic "toString" types of functions).
Created "tangelo.date.*" functions rather than messing with the Date prototype; changed client code to conform.