Properties tab + mutable context roots

Changed the constants files so that the roots are parameterised, and each service has a default map where they can modify this. To change the default per application, go to the managed-beans and modify serviceMappings inside the endpoints. Look at the w3connections bean for an example. 

In the Grids, there was another constructUrl, but here there was no access to the endpoint so the constructUrl and buildUrl methods now take an endpoint as a parameter, if this is present it changes the mapping otherwise it should work the same. 

Also properties tab is now present for entering snippet parameters. It remembers parameters entered so they don't need to be entered multiple times, and if a parameter is missing it informs the user and mentions which parameters are missing. 

The new format for snippet parameters is name=[value][|label=CustomLabel][|helpSnippetId=snippet_id][|required]