FS#4684 - Use shift to estimate costs only with a certain type of commands
This patch makes the shift key more usable by narrowing the set of commands in which we can estimate costs.
For the set I chose CMDT_LANDSCAPE_CONSTRUCTION and CMDT_VEHICLE_CONSTRUCTION commands. These are the only commands that costs us money and after firing them we can see on the map a floating price drawn red (this rule is very clear). Other commands that have to do with our money are CMDT_MONEY_MANAGEMENT, but these are actually costless and cost estimation returns 0 anyway (and we can't see a floating price drawn red after firing them).
The patch is related to (it's a suggestion to) FS4668
This task depends upon