package.json: updated github urls

Changed the home and repository URLs to point to the new node-inspector org.
PageAgent: fix for main script without extension

Fixed a bug where `node --debug app` caused node-inspector to add
a non-existent file `app` into the resource tree.
Overrides: show main app file

Added a startup hook that opens the main application file in case no files
are opened.

Created a public API for embedders, added function buildInspectorUrl().
updated changelog for v0.3.2
started work on v0.3.3