MCT-3902: [Plot] Apply button misbehaves.

- Set listeners for the Point Filter JComponents widgets to enable the Apply button once the value has been modified.
- Setting default for Non-time dropdown Feedtype DN/EU in reset(), selects first dropdown in combo if no persisted setting value. 

Wrote or re-wrote unit tests (Y/N): N
Ran entire suite of unit tests successfully (Y/N): Y
Verified bug fix with the described replication steps or verified the implementation meets the requirement cited (Y/N): Y
Code coverage requirements satisfied (new code=80%, changed code=at least as high as existing) (Y/N): N
Code review date and attendees: Code review by pull request
Describe potential impact on other areas of the code: Plotting
Describe any test prerequisites for this fix (e.g., restart the database): N
For bugs marked "Regression - Yes", describe the cause of the regression:
Did you modify any pom.xml file? If yes, did you thoroughly document your changes and reasons? N