New attribute in the manufacture section of the ruleset: producedItems

For the sake of moddability.

It is a map with name-value pairs. (just like the requiredItems)
If not specified, it contains only one element, which is the name-parameter with the value of 1.
The name specifies the produced object, and the value specifies how many of that object is created. (by completing "one object" of that project)

With this new attribute we can create manufacture-rules - for example - to convert 1 piece of Heavy Plasma Clip to 3 pieces of Elerium-115. (that clip is assembled of 3 pieces of elerium)
Sample ruleset file for this clips -> elerium conversion can be found here: http://openxcom.org/forum/index.php/topic,1623.msg15820.html#msg15820
Changelog updated
Redundant if and c++98 compatibility fixed.
Making one common "for", instead of more, and checking every single produced item if it's a craft.
Check if a produced item is fuel to refuel a craft
Checking the available hangars against the number of crafts beeing built with "one item" of the project.
- Fixed: Check available hangars on the start of a project
- Fixed: Compiler (include) errors
Do not allow to start a manufacture-project with zero units to produce!
Ok, let's limit the number of crafts in a manufacture-project to 1. (per "one item")
Removing some unneeded includes
Merge pull request #740 from fenyo1/ruleManufactureAttr

New attribute in the manufacture section of the ruleset: producedItems