Unify dependency management

[abose]

Modern dependency management

Brackets currently have redundant dep management which is creating unnecessary build complexity. We need to address this. More details can be found here: adobe/brackets#12006 . This is preventing the upgrade of several dependencies to the latest version.

solutions

• Nuke git submodules- done. Copied code as-is for the time being the third party folder. There are no node modules, so safe.
• update mechanism for third party libs is done, we need to use it for all items tracked in this issue: Dynamic upgrade solution for Third party deps #10
• Remove npm-shrinkwrap based package locks to enable node upgrade #9
• Remove defaultExtensions build task #12
• npm-install-extensions grunt task removed
• no-host server is integrated in source, there should be a way to dynamically upgrade it. #31
• Upgrade to ES6 modules #32
• Modernise node  #85
• Update testing framework. #91