Installing, removing a module should clear the Views RSS plugin cache

Problem/Motivation

Installing a new module that adds Views RSS plugins doesn't reset the internal cache of the available plugins.

Proposed resolution

Clear the Views RSS caches when a new module is installed.
Clear the Views RSS caches when a module is uninstalled.

Remaining tasks

Do the thing.

User interface changes

n/a

API changes

n/a

Data model changes

n/a