Add biowdl/tasks test corpus

[mlin]

• typechecker: workflow output expressions can reference previous workflow outputs (Variables in the output section can not be referenced in the output section. #155)
• parser: task 'non-input' declarations can interleave anywhere among other sections (task "pre-output" declarations #156)
• parser: spike in newline at end of input (accommodates last-line comments)
• check: make UnusedDeclaration's heuristic index files exception case-insensitive

[mlin]

@rhpvorderman @DavyCats

In the miniwdl test suite, we embed several public WDL corpi and ensure we parse them successfully and reproduce lint results. Here I've added biowdl/tasks to start with, taking care of a few miscellaneous compatibility issues (including #155).

The main remaining thorn (which I imagine you've observed already) is the use of Object in common.ObjectMd5. Since the miniwdl project started when there was already general consensus to 'violently deprecate' (i.e. delete) Object from the WDL spec, we've been hoping to get away without implementing it at all. So, I wonder if there's any negotiability in the use of Object on your end? 😅

[coveralls]

Pull Request Test Coverage Report for Build 650

• 13 of 13 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 96.104%

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Totals
Change from base Build 643:	0.006%
Covered Lines:	3231
Relevant Lines:	3362

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💛 - Coveralls

[DavyCats]

@mlin I don't think that task has ever been used. It seems like an artifact from the draft-2 days when we were still experimenting with WDL's capabilities and how to set things up. Unless @rhpvorderman has any objections (:stuck_out_tongue:), I will be removing it.

[mlin]

@DavyCats that will be a big relief for us, thanks! Right now the test harness "blacklists" common.wdl and the files that import it, so that the tests don't run and fail on them. Later we'll bump the submodule revision, remove the blacklist, and chase down any remaining issues.

[rhpvorderman]

@mlin
@DavyCats removed object from tasks and I just merged that into the latest develop branch of https://github.com/biowdl/tasks