Extend "can building be built" requirements logic with build queue contents

[lanedirt]

Currenly when trying to build a building the requirements are checked. If the requirements are not fulfilled you cannot add a building to the build queue. However when building multiple buildings via the queue the contents of the queue should be included in this check.

Example: shipyard building requires robotics factory level 2. If you have a new planet and add robotics factory level 1 and level 2 to the queue, then after those are built the shipyard should also be able to be built. But right now when level 2 is in the queue the shipyard is not eligible yet to be built. According to the official game it should be possible to add shipyard to the build queue if level 2 of robotics factory is in the queue.

This also applies to other buildings and also to research.

Todo:

• Extend "requirements met" check for buildings and research: look in the existing build queue and include the to-be-built/upgraded levels in the check.
• Make sure to also add proper checks when a build queue item starts in case previous queue items have been canceled. E.g. it should not be possible to add robotics factory level 1 and 2 to the queue, then add shipyard build order, cancel the robotics factory and still end up with a shipyard. Add double checks: cancellation of item should recalculate the queue and remove any where requirements are no longer met. Additionally add check for when a build queue actually starts processing if requirements are (still) met.

[lanedirt]

Fixed by #421.