* add brightray API to override app version
* in atom browser, use brightray app version API
* on Linux, have GetApplicationVersion() use brightray version API
* on Linux, implement brightray::GetApplicationName()
* fix typo in brightray API
* make browser.GetName() logic follow GetVersion() logic
* improve variable name in OverrideApplicationVersion declaration
* fix typo in brightray impl
I.e., use CFBundleShortVersionString instead of CFBundleVersion on OS X and
ProductVersion instead of FileVersion on Windows.
This is generally more useful (although slightly lower granularity) than the
machine-readable version number.
