ViewTask

- When supplied with a vector of attribute names, can insert spacing into the
  rendered output when values change.  These we call listing breaks.
Context

- Improved sort column parsing to include an optional trailing solidus, in
  addition to the +/- sort direction.
TW-193

- TW-193 Support listing breaks.
Config

- Added listing breaks on the 'project' columns, for the 'list' and 'minimal'
  reports.
TW-1373

- TW-1373 taskrc.vim VIM syntax file updated (thanks to lolilolicon).
Merge branch '2.4.0' of ssh://git.tasktools.org/tm/task into 2.4.0