#200 Move missions to common

[Michael Vehrs]

Units that belong to human players also have orders that may take several turns to carry out, such as go-to, follow trade route, pioneer work, even work-as. Some of these orders could be handled as missions, simplifying the "do work" code. Next, these missions could be extended to provide things like an exploration mission for scouts (and ships) and pioneering missions like "build road from colony A to colony B".

[Mike Pope]

Ticket moved from /p/freecol/restructuring/9/