fixes CB-5806 [Windows8] Add keepCallback support to proxy
CB-5438 Exclude local symlinks from jshint

Both /src/test/androidexec.js and /src/test/iosexec.js are symlinks to
/src/android/exec.js and /src/ios/exec.js

Symlinks don't work on the Windows platform and are represented there as
a text file with the contents being a text description of where it
should be pointing at.

The problem is that the jshint task of the build tries to parse those
'text' files as js files, which fails for obvious reasons.

My solution is to explicitly exclude those 2 symlink files from the
jshint task. The files they point at are included in the src/**/*.js
jshint src setting, so they will get checked anyway.

Now we can succesfully run grunt build on Windows.
Merge branch 'CB-5806' of https://github.com/sgrebnov/cordova-js
Merge branch 'CB-5438' of https://github.com/BBosman/cordova-js
CB-5973 blackberry: add support for sync exec
CB-5973 blackberry: use sync by default
Update exec.js

The spec implies that the last argument of cordova.exec() should be optional.  However, if it is omitted, iOS emits a cryptic NSInvalidArgumentException.  This can be avoided if actionArgs defaults to an empty array.
CB-6007 Fix findCordovaPath() not working when path contains a query param
CB-5438 Remove test symlinks & fix some build errors on windows.
Move all deps into devDependencies.
Add back "grunt btest" command
CB-5438 Use jsdom-nogyp to avoid dependency on python & visual studio