Improvements to the script validating WDLs using miniwdl

[VJalili]

• Take imports dir as an input argument;
• Allow setting max depth of import, and set it to max 2 (compared to max 10 of miniwdl default); # - Improve displaying messages on the console;
• Add tips for debugging errors.

[mwalker174]

Great, this looks fine to me. The max import depth is hard-coded in mini-wdl correct? I see the default of 2 which seems very shallow to me. Also just curious - I may have misheard you at last standup but isn't the max depth 10? Did you actually encounter this anywhere in our repo?

[VJalili]

Thanks for the review @mwalker174. 10 is the default value for max import depth; I am changing the default to 2 mainly to simplify debugging/tracking import errors.

For instance, with max import depth set to 10, the validation process throws an import error validating wdl/AnnoRdPeSr.wdl complaining 'Failed to import VaPoR.wdl', which implies the script cannot find VaPoR.wdl in the import path; while the root cause is in wdl/TasksMakeCohortVcf.wdl with the error Expected Boolean instead of Boolean?.