Initial coding of a transform command to exo.

Takes a dataport, a range, and a function.  Transforms the data by the function.
Merge remote-tracking branch 'upstream/master'
Allow overriding the location of exo plugins by setting and environment variable: EXO_PLUGIN_PATH

Can use : to separate multiple directories to search in.
Added option to save the data before and after the transform.

The file is such that it can be an input to record.
Few more things to ignore.
Merge branch 'envPluginDir'
Use ExoUtilities
Stop if no data was read.
Tested start and end and fixed the differences for flush.
Merge pull request #14 from tadpol/master

Transform Plugin