Unit tests: created the test file for the Image class.

Unit tests use the Google C++ Unit Test Framework (gtest).
Unit tests: modified the Makefile structure to download gtest.
Test makefile: the gtest lib is now automatically built.
uEye camera: added pixel clock related functions.
uEye camera: added and implemented the 'getDefaultPixelClock' method.
Camera class: Added the 'displayInfo' method.

This method displays informations about the camera on the standard
output.
main: Added the -i command-line argument.

This option displays informations about the connected cameras.
NOTE: this is currently really messy and shall be fixed in ulterior
releases.
uEye: Added minimum, maximum and step getters for the pixel clock.

These methods are helper functions that rely on the
'getPixelClockRange' method.
uEye camera: the pixel clock is now set to its minimum value.
Merge branch 'ueye_pixel_clock'
Unit tests: added a test file for the generic utilities.
Unit tests: Modified the test Makefile to compile the utilities tests.
Unit tests: Added a utilities test case.

The new test case tries to extract the extension of a file name with
multiple dots.
Unit tests: added a third utilities test case.

The test tries to extract the extension of a file whose name contains
non-Ascii characters.
Unit tests: began using ASSERT_STREQ instead of strcmp ASSERT.

The Unit test framework provides string comparison assertions.
Unit test: Renamed the UtilitiesTest test series.

All tests referring to file extensions are now labeled as
'FileExtensionTest'.
Unit tests: Added a fixture class for image tests.

This fixture generates a random 800x600 grayscale image. A new test case
was added to check that the Image class writeToPNG method generates a
proper PNG file.
Merge branch 'tests'
Unit tests: Refactored the image test cases for uniformity.
Unit tests: started implementing a PNG comparison.

NOT WORKING.