Solution: log the intentional ignoring of a branch

Notes: I did not find an easy way in the web of calls between
GitHubSCMSource.java#L987 where code begins "Checking branch"
and BranchDiscoveryTrait.java#L230 where it decides the branch
is not good by current strategy, so could not hook into the
TaskListener and log right into the branch indexing run console.

But at least seeing messages in common jenkins.log can help.

Signed-off-by: Jim Klimov <EvgenyKlimov@eaton.com>

…ing()

…he indexing console and not the server log (thanks @bitwiseman)

…d from them

…ranch, so the text line is not unreadably glued to next inspected branch

…hes as of 2020-06-04

…om bitbucket-branch-source-plugin

Per https://bugs.java.com/bugdatabase/view_bug.do;jsessionid=d014dfa686594180be40ca5872f5?bug_id=4907024
When the contents of an @see tag begins with a '<', the tag must be of the form:

    @see <a href="URL#value">label</a>

So we need to either not start with "<" or drop trailing text...

…log-ignored-branches