Download "clean" FCS files

[whitews]

Implement downloading of FCS files with ReFlow channel annotations. This allows a project user to export all the files with a common set of channel names. Also, create a file name convention for the "clean" files that is consistent and contains useful metadata about the file such as the site code, subject code, etc.

[whitews]

1b91c58 closes #19

[whitews]

Need to add the original compensation matrix, if present, to the cleaned FCS file. This is usually stored in the $SPILL metadata key/value.

[whitews]

Added original spillover matrix in 1c4e697

But, the $PnR values need to be set differently to match the original files. A lot of cytometers use 262144 for this value. I'll calculate the max value and set all $PnR values to 262144 if the true max is below that value. If the true value is above, I'll use the real max value.

[whitews]

feature completed in 424718e