Code quality improvements in the local runtime

A pass over the local runtime to improve overall code quality:

**Removed:**
  * Unneeded variables
  * Unneeded keywords
  * Declarations of unthrown exceptions
  * Redundant dependencies in the pom

**Added:**
  * `final` wherever possible
  * Added type parameters where they were missing
  * JavaDoc where it was missing

**Fixed:**
  * Typos