Add Navigation Capabilites

[TTWNO]

• Add signal handlers
• Add capslock+arrow-based navigation
• Handle text cursor cases (the "next" element is not neecesarrily the next in the tree if the user is mid-text)
• Handle text inner items (when navigating, only read up until the object replacement character; if the user wants to continue they can use the "next" action to read the inner item)
• Anti-Feature: caret browsing/flat review. Make the caret controlled purely through Odilia.
• Allow non-capslock prefixed keybindings
  • Allow arbitrary activation keys
  • Ensure no overlap in fuzz testing
• Remove Default impl of keybindings
• Read keybindings from config file (via Odilia, not directly)