QBS uses inconsistent terminology when talking about file names and paths

This is a huge problem in my opinion so I'm marking it as a bug.

We should be very consistent with our use of terminology pertaining to file names and file paths, as improper naming of properties leads to confusion and accidental misuse of the toolset.

We should standardize our usage of the names as follows:

• absoluteFilePath: an absolute path to a file, example "/Users/jake/cube.qbs"

• filePath: an absolute or relative path to a file, example "/Users/jake/cube.qbs" or "../fake/sphere.qbs"

• absolutePath: an absolute directory path, example "/Users/jake"

• path: an absolute or relative directory path, example "/Users/jake" or "../fake"

• fileName: a file name only, without a path, example: "sphere.qbs"

• absoluteFileName: this means nothing. You're fired.

Proper usage of these terms will make it significantly easier for developers to know what type of path they're being given so that it may be handled correctly.