Implement bindsym mouse configuration

If a `bindsym` config directive specifies a symbol beginning with
"button", the binding will be given the type B_MOUSE for the indicated
button number.

Example:

bindsym $mod+button2 exec echo 'button two'

This will be interpreted as having input code (now `keycode`) 2 and type
B_MOUSE.

The mechanism to find and run mouse bindings on mouse events is not
implemented.
Bugfix: ipc window event crash with no window

The log message at the top of ipc_send_window_event would segfault when
no xcb window is present, such as for a split container.

The log now shows the con id which is more relevant anyway.
Delegate click handling to dock clients

Do not handle click events on dock clients because they are not managed
windows. Dock clients are responsible for sending the message to i3 to
focus a workspace if that is appropriate. i3bar now sends the message to
focus the correct workspace when that is appropriate.

Otherwise, it could interfere with the dock clients own click handling,
which could be an action to focus a different workspace than i3 had
assumed, such as would be the case with a workspace widget.
Feature: send complete config on barconfig_update

Send all the options in the bar block on the barconfig_update event.

This will eventually allow for dynamically updating bar colors with the
`reload` command.
Implement the window::fullscreen_mode event

The fullscreen_mode event is a window with the "change" property set to
"fullscreen_mode". This event should be emitted whenever a window enters
or exits fullscreen mode.

This event can be used to turn off dpms off when a window is fullscreen
or display the fullscreen container name in the status line for
instance.
s/he/she/, s/his/her/ (Thanks lasers)