One change order, several PCOs

GCs don't always execute your PCOs one at a time. Three PCOs get rolled into one change order; now the change order says so.

• Pick several PCOs. Creating a change order, tick every PCO it combines. The day impact adds up across all of their change events — a change event on two of them counts once.
• Fix it while it's a draft. Click the PCOs on a draft change order to add or drop one. Once the change order is executed, its PCO list is locked with the rest of it.
• Pending stays honest. Every PCO on a change order leaves the pending number on the project overview — no more counting the folded-in ones on top of the change order.
• Everywhere it shows. The Changes log, its CSV, the printable Change Order Log, and the budget's change-order cost all read every PCO on the change order.