Fix #148: BASE var default should be the workflow directory
refactor for cleaner use of figure-workflow-file
Correct default BASE var to be workflow dir not workflow file
Allow backslash at end of line as continuation.

backslash+newline is now equivalent to a space.
Fix small typo in default targetv

Switches the default targetv from ["=..."] to ["..."] in clj-frontend/run-workflow.
Merge pull request #149 from morrifeldman/targetv-typo

Fix typo in default targetv in clj-frontend/run-workflow
Revert #149 and constantize default targetv
Make clj_frontend use core/DEFAULT-TARGETV constat