[PATCH] Extension of the pair tech mechanism to allow both of them to be researched, but at different moment

[mimo]

One of the main criticism of the present tech pair implementation is that choices are definitive and can no more be changed afterwards, even if the player's strategy may change. This patch contains an extension of this pair mechanism allowing both techs of a pair to be researched, but with additional requirements (for example it could require the next phase, or any additional other tech).

The needed changes in the templates are:

in the pair template, "researchBoth": true in the tech templates, "pairRequirements": { the requirements if not selected first} and "pairRequirementsTooltip": "the corresponding tooltip"

In the patch, I've put two examples of such pairs to show how we can give additional choices to the player, instead of fixing the moment at which each tech is available.

In the gui, when hovering over any of the two techs, there is a red cross overlay on the other tech. When both techs can be researched, the cross will be orange.

[mimo]

to be put in art/textures/ui/session/icons

[Imarok]

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