Weak Suffixes Map

Add ability to specify "weak" suffixes for technology.

Usual behavior for technology suffixes is considered to be strong-binding, i.e. when dependency item has no technology specified, any file that matches (item path + any suffix for building technology) is included in sources file list.

Another kind of behavior is added, which is considered to be weak-binding -- suffixes that are weak don't add files to source files list, unless technology matching the weak-suffix is explicitly specified in the dependency item.