Specify arbitrary numerical values in the gamesetup

[elexis]

Currently the gamesetup options are either checkboxes or dropdown lists, i.e. limiting the choice to a dozen of hardcoded values. Many settings however are numerical values, thus could offer a much greater variety of choices. For example:

• The ceasefire or wonder timeout is a number in minutes
• Starting resources: #4379.
• Population capacity (if we don't cap it to 300, there should be a yes/no question when exceeding)
• Gamespeed (same about cap)

The options page (observer limit) demonstrates that the existing text GUI objects are sufficient to implement this (with the exception of #4380).

[Imarok]

Move tickets to Game Setup as UI & Simulation got some sub components.