do not add elektra as dep for resolver variants

fixes #23
add test to silently ignore when no tty is found
fix tty check
fix tty check
depend on cmake 2.8.8

OBJECT libraries need it
fixes #60
attempt to fix NULL ambiguity

remote debugging for build server error:
/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/RelWithDebInfo/gcc_version/4.4/plugins/ALL/source/src/bindings/cpp/examples/cpp_example_hierarchy.cpp:180:
error: call of overloaded ‘Key(int)’ is ambiguous
/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/RelWithDebInfo/gcc_version/4.4/plugins/ALL/source/src/bindings/cpp/include/key.hpp:287:
note: candidates are: kdb::Key::Key(std::string, ...)
/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/RelWithDebInfo/gcc_version/4.4/plugins/ALL/source/src/bindings/cpp/include/key.hpp:262:
note:                 kdb::Key::Key(const char*, ...)
/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/RelWithDebInfo/gcc_version/4.4/plugins/ALL/source/src/bindings/cpp/include/key.hpp:248:
note:                 kdb::Key::Key(const kdb::Key&)
/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/RelWithDebInfo/gcc_version/4.4/plugins/ALL/source/src/bindings/cpp/include/key.hpp:220:
note:                 kdb::Key::Key(ckdb::Key*)
Fixed a memleak in the metamergestrategy test #56
do not depend on text output of tty program
add memleak property again because #32 is not fixed
NULL fails on gcc 4.{6,8,9}
fix shadowing

/var/lib/jenkins/jobs/elektra-multiconfig-gcc-stable/workspace/build_type/Debug/gcc_version/4.6/plugins/DEFAULT/source/src/libelektra/keyset.c:1060:9:
warning: declaration of ‘index’ shadows a global declaration [-Wshadow]
improve tty searching
add todo
fix bogus cmake warning
swig-python: it's PYTHON_INCLUDE_DIR, not PYTHON_INCLUDE_PATH

see cmake bug #9508