Removed unnecessary convenience initializers.

[OrkhanAlikhanov]

#1085
Removed all redundant convenience initializer:

public convenience init() {
  self.init(frame: .zero)
}

Only kept in TextView because it has some logic there:

Material/Sources/iOS/TextView.swift

Lines 233 to 247 in 06d223d

	/// A convenience initializer that constructs all aspects of the textView.
	public convenience init() {
	let textContainer = NSTextContainer(size: .zero)
	let layoutManager = NSLayoutManager()
	layoutManager.addTextContainer(textContainer)
	let textStorage = TextStorage()
	textStorage.addLayoutManager(layoutManager)
	self.init(textContainer: textContainer)
	textContainer.size = bounds.size
	textStorage.delegate = self
	}