Allow recursive includes in tree (JSON) files

Prior we only allowed for one include in our json file inputs.  Now
these files can recusively include more than one.  This is handled
in the flattenjsoninclude function

taskbase.py
    - flattenjsoninclude is now recursive
    - it requires the includefile name as an arg input
Merge pull request #40 from baude/jsoniterate

Allow recursive includes in tree (JSON) files