This commit changes mouse-based selection and middle click to use the
PrimarySelection.
CTRL-SHIFT-{C,V} use Clipboard.
{SHIFT,CTRL}-Insert use PrimarySelection.
`CompleteSelection` and `CompleteSelectionOrOpenLinkAtMouseCursor` now
require a parameter to specify the destination clipboard.
Removed the `default_clipboard_XXX` options added in
8dad34fa61 in favor of just explicitly
assigning the key/mouse bindings.
closes: #417
* Adds `CopyTo` and `PasteFrom` assignments that specify the
destination/source.
* Adds `default_clipboard_copy_destination` and `default_paste_source`
config options that specify the default destination/source for
existing `Copy` and `Paste` operations (for @bew)
* Deprecating `PastePrimarySelection` in favor of `PasteFrom`.
* Added `CTRL-Insert` -> `Copy` (for @Babar)
Aside from the new key assignment, these changes shouldn't change
the default behavior, but do make it easier to consider changing
that in a later commit.
They should allow for example:
* Set `default_clipboard_copy_destination = "PrimarySelection"` to
prevent populating the clipboard by default when using the mouse.
* Overriding the CTRL-Insert, CTRL-SHIFT-C to explicitly populate
the clipboard
* Set `default_paste_source = "PrimarySelection"` for middle click
to paste the selection.
* Overriding SHIFT-Insert, CTRL-SHIFT-V to explicitly paste from
the clipboard.
refs: #417
