[CMake] cmake/ccmake - use current dir on default

[Brad King]

Jens wrote:
> It would be great if cmake and ccmake would search for a CMakeLists.txt in the 
> current directory on default.
> 
> Instead of "ccmake ." you could simply write "ccmake".
> It would be much easier to explain others how to compile.

Running with no arguments produces help.  If it had different behavior 
depending on the contents of the current working directory it would be 
confusing.  Imagine also if there happened to be a CMakeLists.txt file 
in someone's home directory and they ran cmake their to see the help. 
Then they would end up with a bunch of build tree stuff in their home 
directory.  Also the feature would only work for in-source builds which 
are not recommended anyway.

-Brad