Allow to use multiple technologies as requirements for unit training and construction.
Track of important files:
globalscripts/Templates.js
gui/common/tooltips.js
gui/session/selection_panels.js
components/GuiInterface.js
components/Identity.js
components/TechnologyManager.js
ai/common-api/entity.js
ai/common-api/gamestate.js
ai/petra/queueplanBuilding.js