css: round both corners of search entry
css: make linked entry/scrollbar styling more consistent
GbEditorFrame: invalidate textview contents after saving document.
GbSourceView: invalidate text window when font changes
credits: include version in credits screen
GbEditorDocument: release doc sequence id on finalize
settings: add setting to overwrite braces.
GbSourceView: allow overwriting braces like } ) ] ' and "

This can be handy instead of having to move over the character with
arrow keys and such.
settings: add overwrite-braces to settings widget
css: adjust commandbar styling to only stay dark on entry box
GbSourceView: add option to insert a matching "'}]) on key press
GbEditorSettingsWidget: plumb setting for insert-matching-brace
GbEditorSettingsWidget: make things a bit more succinct.
defaults: update language defaults
add some notes to the README
style: make current-line slightly translucent
GbSourceView: ignore matching brace insert in a few cases
GbEditorFrame: keep cursor on screen when performing scroll actions
GbSourceView: support deleting matching characters on backspace

Backspace from "|" will delete both quotations if insert-matching-brace
property is set.
GbSourceView: ensure key-press triggers auto-indent during overwrite