Allow to define runtime "_" in configuration file

[tomalec]

Related to #79

[rafalwrzeszcz]

Well, I was the one to implement merging of runtime and conffile options and I left this case without solution because of such... not very elegant solutions :).

I see the need of such feature, but I'm not fully convinced by your path... the problem is that console options module pre-defines _ argument as empty array, so it's always present. Maybe we should merge them instead?

But if noone else sees the problem, then nevermind my comment, I have nothing against that, just pure elegancy :).

[tomalec]

You're right, it's not so elegant.

It was first, simplest solution for my problem, but merging those arrays seems much nicer.

[tomalec]

Do you think it's nicer?
BTW. I wasn't sure. Does order of files in _ makes any difference?

[rafalwrzeszcz]

Sure, a lot more elegant :).

Order of files can only change the order of occurance of entities with same name in resultet documentation - all source files are first scanned for symbols, symbols are not aware of code dependencies, also in JSDoc3 names don't collide since documentation is generated for all symbols (even with repeated names).