About testcase archives

[Ivan Glushkov]

Good day.

I've just closed i#188 "consolidate test repositories".
While working on it i've removed all archives except "a.gz", so now
all testcases are built from it.

Also i've added some functionality to "dttest" module:
- commit_local_issue() - returns the id of new issue
- last_rev() - returns last svn revision of database
- info() - idea of this function was to get all possible information
about database. In the current moment it just allows to find the
number of issues in database. I suppose later we'll add smth else.

also changed
- wc_replace(). it's now possible to pass negative revision number
(so it'll be substituted from the current revision).
- new_issue() now returns the id of new issue.

So it's now possible to create tests that shouldn't be modified on
changing testcase archive.
Some simple rules on creating new testcases:
1. Testcases should not depend on the current revision of the database
in a.gz. last_rev(), wc_replace() with the negative revisions should
help in it.
2. Testcases should not depend on the _all_ issues in database.
Because when new issues will be added into it your testcase should be
changed to pass all the tests.
It's possible though. Use filters that will show only first 5 issues,
for example, with Category=sample-category2 (this will require that
all new issues in database will have different Categories)
3. While adding new issues in database make sure they don't belong to
simple-category (see previous clause)

Ivan.

p.s: Sorry for the so large last commit. I just wasn't able to split
it into the little parts.