extern'ing LP_QUERY_JS to suppress downstream (in calabash-ios-server) compiler warning

## Motivation

The calabash-ios-server project uses this repo as a submodule.  The LP_QUERY_JS static declaration/assignment is throwing a compiler warning in that project.

@krukow

I have got to ask - why is the CalabashJS/CalabashJSLib/LPWebQuery class in this project?  

This code will not compile because it depends on two objc classes that do not exist in this project:

* LPJSONUtils
* LPTouchUtils

I am not even sure why would want to compile this project...

Can the LPWebQuery files be migrated to calabash-ios-server?

Or should the LPJSONUtils and LPTouchUtils be migrated to here?