updated FindPython.cmake

added Python27 to the FindPython.cmake Module
added a uint32 template for vil_threshold
added a warning to vpgl_load_proj_camera_process

Added a warning to vpgl_load_proj_camera_process.cxx when, after parsing a camera file, there is more text left to parse. This could indicate that the camera file is not of the correct type.
corrected documentation/variable names
updated the vcl_args to require a scene file
a bug fix

The wrong process was being initilized for the BOXM2_GAUSS_RGB scene type.
bug fix for the var_img calculation

The calculation of variance was incorrect. Was sum_X(x_i^2 * prob^2) - (sum_X(x_i*prob))^2. Should be sum_X(x_i^2 * prob) - (sum_X(x_i*prob))^2. It also should have been re-weighted by sub_block_dim, as the mean calculation was.