TRUNK-4015: Application data directory should include web app name

https://issues.openmrs.org/browse/TRUNK-4015

Added feature to create different app data directory for different web apps as per the discussion in the ticket
Set log4jExposeWebAppRoot to false so to avoid webAppRootKey clashes per web app

Set default database name to webapp name e.g. test-deploy.war results into a database called test-deploy.
Looking at spring documentation at [Log4jWebConfigurer](http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/util/Log4jWebConfigurer.html), the default behavior is to expose it, therefore it is useless to add this line unless you wanted to set its value to false.  Exposing it means that log4j can write to log files relative to the web app root. 

But there is a warning on that page that says:
Some containers (like Tomcat) do not keep system properties separate per web app. You have to use unique "webAppRootKey" context-params per web app then, to avoid clashes.

To me, this implies you also need to set the context-param for webAppRootKey so that differs for each webapp for this to work in tomcat, did you test out things well to ensure that logs are written to separate files for each web app?