Modifications made primarily to fix issues encountered with SC, MSC, and SM.  However, these issues were encountered during the implementation of other modifications, so this commit includes several other additions/modifications:

SC/MSC/SM Changes:
- Reduced SC/MSC/SM memory consumption by removing unnecessary intermediate variables
- Removed issue with -INF and avoided possible issues with INF/NAN discrepancies by forcing SC/MSC/SM delta values to positive values (including INF).
- Removed discrepancy between voxel # calculated manually and by mod function when position is on edge between voxels by converting variables to double precision
- Removed issues with voxel walking when slope is steep or flat due to numerical precision (rounding/truncation) by converting relevant variables to double precision.
- Added safeguard to prevent movement in a direction where x/y/z entry and exit positions are the same (results in division by 0) by setting movement direction to 0 in this case.

Other Changes:
- Added GPU kernel to perform backprojection, combining FBP filter/backprojection function calls into a single function
- Separated FBP image to hull process into separate optionally executed function (host or GPU)
- Removed allocations/initializations of variables used for standard deviation calculations from initialization function and placed these in a separate initialization function to be called immediately before required
- Added function to write WEPL data for each bin to file for later analysis (still may need work)
- Added function to write binary input data to text data file
- Began developing function to convert u/t/v coordinates to x/y/z coordinates so this process can be separated from reconstruction volume intersection function which may no longer be necessary.  By separating the coordinate conversion, the intersection function can still be ran but the program will still function properly if it isn't.
- Added device function for converting x/y/z positions to x/y/z voxel #s
- Added function to determine how far into a voxel a position is (for use in voxel walking)
- Created enumerated type for the possible filters to use in FBP and added parameter to specify which one to use.
- Added parameter for the value of 'tau' used in Ram-Lak (ramp) filter.