mv ThirdParty, 3rdParty -> 3rdparty for consistency with other projects

3rdparty/Core/CMakeLists.txt

3rdparty/Core/cerfcpp.h

3rdparty/Core/tspectrum/CMakeLists.txt

3rdparty/Core/tspectrum/README.md

3rdparty/Core/tspectrum/TSpectrum2.cxx

3rdparty/Core/tspectrum/TSpectrum2.h

3rdparty/Core/tspectrum/spectrum_types.h

3rdparty/Core/tspectrum/tspectrum.cxx

3rdparty/Core/tspectrum/tspectrum.h

3rdparty/GUI/qcustomplot/CMakeLists.txt

3rdparty/GUI/qcustomplot/GPL.txt

3rdparty/GUI/qcustomplot/changelog.txt

3rdparty/GUI/qcustomplot/qcustomplot.cpp

3rdparty/GUI/qcustomplot/qcustomplot.h

3rdparty/common/CMakeLists.txt

3rdparty/common/gtest/00_PROVENANCE

3rdparty/common/gtest/CMakeLists.txt

3rdparty/common/gtest/gtest-1.10.0/.clang-format

3rdparty/common/gtest/gtest-1.10.0/.gitignore

3rdparty/common/gtest/gtest-1.10.0/.travis.yml