Cleanup of interface definitions for webapp entities

- All fields are `public static final` and all methods are `public abstract` in Java interfaces so I have been removing superfluous declarations from the `software/webapp` entities.
- I also removed several duplicated `AttributeSensor` and `ConfigKey` definitions from the `TomcatServerImpl` since these should only be defined by the entity interface.

The currently failing integration tests seem to be being caused by the presence of the duplicate **install.version** `ConfigKey` with the old value of _7.0.34_ in `TomcatServerImpl` which has been removed as noted above.