This implements the following:
* `floating_modifier` configuration directive
* Drag a floating window by its title bar
* Hold mod + drag a floating window from anywhere
* Resize a floating view by dragging the border
* Resize a floating view by holding mod and right clicking anywhere on
the view
* Resize a floating view and keep aspect ratio by holding shift while
resizing using either method
* Mouse cursor turns into resize when hovering floating border or corner
This PR changes the way we handle transactions to a more simple method.
The new method is to mark containers as dirty from low level code
(eg. arranging, or container_destroy, and eventually seat_set_focus),
then call transaction_commit_dirty which picks up those containers and
runs them through a transaction. The old methods of using transactions
(arrange_and_commit, or creating one manually) are now no longer
possible.
The highest-level code (execute_command and view implementation
handlers) will call transaction_commit_dirty, so most other code just
needs to set containers as dirty. This is done by arranging, but can
also be done by calling container_set_dirty.
* The arrange_foo functions are now replaced with arrange_and_commit, or
with manually created transactions and arrange_windows x2.
* The arrange functions are now only called from the highest level
functions rather than from both high level and low level functions.
* Due to the previous point, view_set_fullscreen_raw and
view_set_fullscreen are both merged into one function again.
* Floating and fullscreen are now working with transactions.
When moving focus left or right to an adjacent output, only select the
first or last child in the new workspace if the workspace's layout is
horizontalish. If it's a verticalish layout, use the last focused
container.
* Add and use lenient_strcat and lenient_strncat functions
* Rename `concatenate_child_titles` function as that's no longer what it
does
* Rename `container_notify_child_title_changed` because we only need to
notify that the tree structure has changed, not titles
* Don't notify parents when a child changes its title
* Update ancestor titles when changing a container's layout
* Eg. create nested tabs and change the inner container to stacking
* No need to store tree presentation in both container->name and
formatted_title
Replaces arrange_windows() with arrange_root(), arrange_output(),
arrange_workspace() and arrange_children_of().
Also makes fullscreen views save and restore their dimensions, which
allows it to preserve any custom resize and is also a requirement for
floating views once they are implemented.
