Locator framework

Add a new engine locator framework for searching for engines on the
disk. Changes the implementation of the CordovaEngineProvider so that it
uses the framework to locate the available engines. Introduces
PlatformLibrary to keep track of the locations together with the
HybridMobileEngine instances so that they can be located anywhere.
bug JBIDE-16408 - Use hybrid mobile engines from local directories

Adds a search feature to the AvailableCordovaEnginesSection to look for
Cordova engines on a given local directory. Also improves the UI so that
the locations of the engines are displayed
Error handling for the search

Hooks the StatatusManager to the error that may happen during local
engine
search.
Remove Cordova Engines

Adds a remove button to AvailableCordovaEnginesSection. Deletes an
engine managed by the IDE completely.
bug JBIDE-16579 - Warning " Please select a Hybrid Mobile Engine " is
displayed always

Resets the error message in addition to message.