Code refactor for readability

[GermanAizek]

@darksylinc minor changes affect readability code, but clear() function cleans string correctly

[darksylinc]

Although this has a moderate amount of subjectivity, not every change improves readability. In fact it can make it worse.

For example this:

response = "";
// or this:
binOptList["-O"] = "";

With no context tells me that response and binOptList["-O"] are very likely a string. And that we want to initialize them to an empty string. There's a slight chance it could be a custom class that overrides the = operator for strings, but this chance is very minor.

However this:

response.clear();
// or this:
binOptList["-O"].clear();

Doesn't tell me anything. These variables could be a vector, a map, a list, a string, a custom class. Without an IDE and further reading I can't tell. Is response supposed to hold a list of responses? Binary responses?

There are cases such as in OgreScriptLexer.cpp where the change may likely result in higher performance, and it is a place where performance is important, hence the change is welcome.

Likewise in D3D11HLSLProgram::setTarget it is clearly obvious from context that we are dealing with strings, so mTarget.clear(); is probably better (subjective).

Now variable.empty() vs variable != "" is far less controversial, because the information conveyed is already enough (the fact that variable is empty) and in most places the fact that it is a string is also inferred from context easily (e.g. assert( ( profileName != "" ) && ( "Profile name can't be an empty string" ) ); is obvious). Additionally, variable.empty() covers more cases than variable != "" (when the string is corrupt, and avoids bizarre errors such as zero-length spaces creeping into the source code)

I can extract some of these changes selectively from your PR and merge them manually; so that we can debate the rest.

[GermanAizek]

@darksylinc,
I understood about readability with ur examples and I worsened it. I don't mind if you accept some changes, I'm making an offer, and yours to accept or refuse.