HPCC-12062 Add FromJSON function to ECL

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
right.  So to clarify on eclhelper versioning, and "forward" vs "backward" compatibility. 

I think moving the virtual down would mean that old workunits can still run.

But a new workunit that used fromjson could not run if copied or rolled back to an older release.

Do both forward and backward compatibility require incrementing the eclhelper version(s)?