rosa svn-post-commit: handle edge cases

Tested and modified for correctness and old edge cases.

Separated the create and load logic from `rosie.db` into a new
`rosie.db_create` module. Fixed most `pep8` and `pylint` issues.

Modified `rosie.db_create` to use `rosie.svn_post_commit` directly
instead of via the command line.

rosa db-create: print progress to terminal while loading.
rosa db-create: fix terminal output format
t/rosie.db: fix Python import
Merge pull request #1472 from matthewrmshin/rosa-svn-post-commit-edge-cases

rosa svn-post-commit: handle edge cases
config process: file: handle symlink w/o source

Print a nicer error message when source is missing in a file
installation in symlink mode.