Fix: SwiftLint errors and warnings

[nethraravindran]

This PR enforces Swift style and conventions based on https://github.com/realm/SwiftLint and violations for following rules has been fixed.

• Closing Brace Spacing
• Closure Spacing
• Colon
• Control Statement
• Empty Enum Arguments
• Empty Parameters
• Empty Parentheses with Trailing Closure
• Identifier Name
• Implicit Getter
• Implicitly Unwrapped Optional
• Mark
• Multiple Closures with Trailing Closure
• Redundant Nil Coalescing
• Redundant Void Return
• Switch and Case Statement Alignment
• Trailing Closure
• Trailing Comma
• Trailing Semicolon
• Trailing Whitespace
• Vertical Whitespace
• Vertical Whitespace Between Cases
• Vertical Whitespace before Closing Braces
• Vertical Whitespace after Opening Braces
• Void Return

Rules Ref: https://github.com/realm/SwiftLint/blob/master/Rules.md

[ianpartridge]

Did you mean to rename this?

[nethraravindran]

@ianpartridge Yes, by rules it can contain only alphanumeric characters.