command-bar: Use binding set for complete keybinding

This seems cleaner.

https://bugzilla.gnome.org/show_bug.cgi?id=740659
command-bar: Add commandline history

https://bugzilla.gnome.org/show_bug.cgi?id=740659
start abstracting single editor into GbEditorFrame.
add source change monitor to document, gutter to frame
editor: add an extra line of padding so right margin aligns
Revert "command-bar: Add commandline history"

This reverts commit 962416a459c1d124dea567a5861395e42135565b.
Revert "add source change monitor to document, gutter to frame"

This reverts commit 83ebc410f2c8196bf34477c2d0e9cce3dcbec6e7.
command-bar: Add commandline history

https://bugzilla.gnome.org/show_bug.cgi?id=740659
Revert "start abstracting single editor into GbEditorFrame."

This reverts commit 5a6f23502e3b69c1f69647cd5d327dd36920bffa.
vim: special case 'dd' on last line of the buffer.

This helps us work around some difficulties in how GtkTextBuffer works
since there is no way to select the beginning of the following line in
the buffer.
gtk: within_margin should be a double.
seq: add document sequence to track unsaved file number
GbTabStack: add stack container for new style tabs
build: add doc sequence to build
GbTabGrid: add tab grid for grids of GbTab
vim: add jump-to-doc signal for SHIFT+K
vim: ignore mark_set() if we are not the focused widget
vim: use connect_object() for object lifetype tracking
vim: don't capture Escape so snippets can handle the signal
tab: use single bit for boolean