Changed NurikabeCell.java from if/else to switch statements

[ErinCohenGH]

Description

Updated NurikabeCell.java to change any nested if/else statements with more than 2 options. Checked whether NurikabeCell and ShortTruthTableCell could be updated from extending GridCell as an Integer to extending as enum. Nurikabe was determined to be better left as an Integer. ShortTruthTable did not need any edits - it had been written as extending an enum, but the issue had not been marked as done by anyone previously.

Fixed merge issue so that using .getElementID instead of .getElementName

Closes #139

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (improvement to an already existing feature)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

No error flags in IntelliJ. Tried playing puzzle file of Nurikabe that utilizes all rules - no issues or bugs. Ran just like it did prior to any changes.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes