refactor: rename RDReaderView -> RDEpubReaderView, update pod config and docs

- Rename source module from RDReaderView to RDEpubReaderView
- Move all source files from Sources/RDReaderView/ to Sources/RDEpubReaderView/
- Update podspec: RDReaderView.podspec -> RDEpubReaderView.podspec
- Update Podfile, demo project, and CocoaPods config for new pod name
- Delete old RDReaderView pod support files from ReadViewDemo/Pods
- Add new RDEpubReaderView pod support files
- Update documentation (API ref, architecture, UML, conventions, etc.)
- Add FixedLayoutRotationTests
- Update .gitignore: exclude .DS_Store, manual unpack backups, _ssoft-output

Sources/RDEpubReaderView/ReaderView/RDEpubReaderContentCell.swift

@@ -0,0 +1,35 @@
+
+import UIKit
+
+class RDEpubReaderContentCell: UICollectionViewCell {
+
+    private var _containerView: UIView? = nil
+
+    var containerView: UIView? {
+        set {
+            guard newValue !== _containerView else { return }
+            _containerView?.removeFromSuperview()
+            _containerView = newValue
+            if let containerView = _containerView {
+                contentView.addSubview(containerView)
+                setNeedsLayout()
+            }
+        }
+        get {
+            return _containerView
+        }
+    }
+
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        _containerView?.frame = CGRect(x: 0, y: 0, width: contentView.frame.width, height: contentView.frame.height)
+    }
+
+    override init(frame: CGRect) {
+        super.init(frame: frame)
+        accessibilityIdentifier = "epub.reader.content.cell"
+    }
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}