Port Longturn patches - game mechanics tweaks with server options (misc)

[daavko]

This is a breakout issue from #503 to track status better.

This is only for miscellaneous game mechanics tweaks that have a new server option or a ruleset option associated with them.

Short summary of patches Miscellaneous tweaks with server options, see commit messages listed below.

Patches to port Commits listed chronologically, beginning from the oldest one.

• longturn/freeciv@f99fff09e1 - Add server setting to mask timeout each turn by a random offset
• longturn/freeciv@983bd92f03 - Add percentage modifiers to global warming and nuclear winter rates
• longturn/freeciv@0f6ef92333 - Add server settings for chance of losing inciting money
• longturn/freeciv@399cc69e97 - Add a multiplier option for spaceship travel time