Now that the dispatcher does its own TryExecute, filters do not need to
do that. This change requires all worklets called by filters to be able
to execute without knowing the device a priori.
Rather than force all dispatchers to be templated on a device adapter,
instead use a TryExecute internally within the invoke to select a device
adapter.
Because this removes the need to declare a device when invoking a
worklet, this commit also removes the need to declare a device in
several other areas of the code.
This commit adds a worklet and a filter to compute
signed integral measures of cells.
It also begins the practic of adding a markdown
changelog entry in `doc/changelog`. See the
changelog entry for details.
