* GTest will be downloaded as external project if needed

* Added readme.

* Fixed bugs

* some small improvements and bug fixes

handle header without extension

handle objeclib only input for target

if compiler num is 0 this is not always an error,
as that  can also happen, when having only a objectlib
as input and no other source files.

Fix unclear error while accidentally sanitizing interface library

Interface libraries added since CMake 3.0 version have INTERFACE_SOURCES property instead of SOURCES so it leads to error which is unclear and prevents project from compiling. Warning would be enough it this case.

Fix language detection with file names containing more than one dot