An option to disable automatic issue creation when build does not succeed

[kumlali]

gogs-branch-source plugin automatically creates an issue when build does not completes successfully (unstable, failure, aborted, etc.).

I have added auto-create issue option which lets users to disable automatic issue creation: PR #11.

[kumlali]

By using SQLiteStudio I executed following SQL commands on SQLite database to disable issue tracking, to delete all the issues and to delete all the actions created for build failures.

-- Disable issue tracking of all repositories
SELECT * FROM repository WHERE enable_issues = 1;
UPDATE repository SET enable_issues = 0 WHERE enable_issues = 1;

-- Delete issues and issue-user dependencies
SELECT name, num_issues FROM repository WHERE num_issues > 0;
DELETE FROM issue WHERE id > -1;
DELETE FROM issue_user WHERE id > -1;
UPDATE repository SET num_issues = 0;

-- Delete actions recorded for Jenkins failures (op_type=6)
SELECT op_type, content, act_user_name FROM action WHERE op_type = 6;
DELETE FROM action WHERE op_type = 6;