Add PyCharm project config files
Stop storing UUID in SQLite database

Instead of storing repository UUID in SQLite database,
just calculate it on the fly from repository base url.
Drop trunk/branches/tags configurability

It doesn't make any sense to change standard
SVN trunk/branches/tags directory layout, especially
given the fact that git_svn_server isn't ready for this.
Drop customizable auth methods

We only support CRAM-MD5, there is nothing to
configure here
Drop customizable realm string

Base url is more than enough
Stop storing repository creation time in SQLite

Nobody actually cares about repository creation time,
so just use start of epoch.
Remove `meta` SQLite table

`meta` SQLite table isn't used by anything now
get-dir: handle None created-by

created-by can be None when repository has
no tags/branches and tags/branches directory
listing is requested
ls-tree: handle None sha1

sha1 can be None when repository has
no tags/branches and tags/branches directory
listing is requested
get-props: handle get-props request on repository root