3586: Set job priority column default to '0', add NOT NULL constraint.
3586: Set priority to "0" if nil.  Fix test fixtures.
3586: Migrate "priority" column so it is an integer instead of as string.
3644: Switched around command line parameters a bit.  Will default to --home
now.  Renamed GroupsDirectory to HomeDirectory and GroupDirectory to
ProjectDirectory.
3644: More renaming GroupDirectory to ProjectDirectory, removing name links.
3644: Working on adding timestamps
3550: Improve startup time by removing excess api client instantiation.
3550: Add --run-jobs-here flag to arv-run-pipeline-instance.

Run new jobs locally with arv-crunch-job instead of asking
crunch-dispatch to run them.
3644: Project and Home directory work.  Added support for returning correct
timestamps on projects, collections, files.  Should be update
CollectionDirectory if the underlying collection record changes.  Fixed bugs.
3644: build_project_trees method ported from workbench, needs testing
3453: Add support for --images to get a list of available images.  Add support
for --project-uuid to place the image and tags in the specified project.  Set a
more useful name for the collection containing the image.
Merge branch 'master' into 3586-job-priority

Conflicts:
	services/api/db/structure.sql
3644: Shared project list almost works, still debugging.
3644: HomeDirectory and ProjectDirectories work, added filename sanitization.
3644: Collections work again, added .portable_data_hash and .manifest_text
virtual files to detect if a directory is a collection.
3644: Re-added support for files with json contents of arvados objects.
Changed block size reported by getattr() use 512 byte blocks which is seems to
be necessary to get 'du' to compute the right results.
3644: Default mount mode now includes home, shared, by_hash, and by_tag.
3654: add "combine selections" option to project#show page.
3644: Tested, fixed various mount modes.
3644: Tweak CollectionReader manifest text regular expression to use multiline
match.