Add test macros for equality/nearness checks

[taketwo]

This pull request adds a family of macros that mimic the style of native google test macros for floats, but act on PCL points:

• EXPECT_XYZ_EQ(expected, actual)
• ASSERT_RGB_EQ(expected, actual)
• EXPECT_NORMAL_NEAR(expected, actual, abs_error)
• ...

These macros are meant to replace checks like:

EXPECT_FLOAT_EQ(p1.normal_x, p2.normal_x);
EXPECT_FLOAT_EQ(p1.normal_y, p2.normal_y);
EXPECT_FLOAT_EQ(p1.normal_z, p2.normal_z);

or

EXPECT_EQ_VECTOR(p1.getNormalVector3fMap (), p2.getNormalVector3fMap ());

with a single less convoluted statement:

EXPECT_NORMAL_EQ(p1, p2);

When such an assertion fails it provides output similar to that of google test macros:

Value of: (p2).getNormalVector3fMap ()
  Actual: 1.1000000238418579 2 3
Expected: (p1).getNormalVector3fMap ()
Which is: 1 2 3