TextView: Update navigation shortcuts

* Command+Left goes to beginning of line, ignoring softwrap
* Command+Right goes to the end of line, ignoring softwrap
* Home goes to beginning of line, accounting for softwrap
* End goes to end of line, accounting for softwrap
* Option+Left goes to previous word
* Option+Right goes to next word
* Command+Home and Command+Up go to beginning of document
* Command+End and Command+Down go to end of document

Shift with any of the above also selects the text.

This is similar to how the text editor Eddie works.

headers/os/interface/TextView.h

@@ -292,10 +292,10 @@ private:
 
 			void				_HandleBackspace();
 			void				_HandleArrowKey(uint32 arrowKey,
-									bool commandKeyDown = false);
+									int32 modifiers = -1);
 			void				_HandleDelete();
 			void				_HandlePageKey(uint32 pageKey,
-									bool commandKeyDown = false);
+									int32 modifiers = -1);
 			void				_HandleAlphaKey(const char* bytes,
 									int32 numBytes);
 
@@ -382,6 +382,9 @@ private:
 			int32				_NextInitialByte(int32 offset) const;
 			int32				_PreviousInitialByte(int32 offset) const;
 
+			int32				_PreviousLineStart(int32 offset);
+			int32				_NextLineEnd(int32 offset);
+
 			int32				_PreviousWordBoundary(int32 offset);
 			int32				_NextWordBoundary(int32 offset);
 
@@ -449,9 +452,15 @@ private:
 			float				fMinTextRectWidth;
 			LayoutData*			fLayoutData;
 			int32				fLastClickOffset;
+
+			bool				fInstalledNavigateLinewiseShortcuts;
 			bool				fInstalledNavigateWordwiseShortcuts;
+			bool				fInstalledNavigateDocwiseShortcuts;
 			bool				fInstalledNavigateToTopOrBottomShortcuts;
+
+			bool				fInstalledSelectLinewiseShortcuts;
 			bool				fInstalledSelectWordwiseShortcuts;
+			bool				fInstalledSelectDocwiseShortcuts;
 			bool				fInstalledSelectToTopOrBottomShortcuts;
 
 			uint32				_reserved[6];