prevent possible indefinite HTTP request loop

- when Gerrit returns HTTP status code 401, the client sends the same credentials forever
- Gerrit returns 401 for example in case of unavailable database
- now the same credentials are just sent once per request
bump version to v0.6.2-SNAPSHOT

- update changelog
update httpclient to v4.3.2
optimize review comment dialog

- use text editor with spell checking
- set better initial size

Resolves #50
optimize change detail panel

- show review status
- show CC'ed reviewers (only newer versions of Gerrit)
- scroll to top when displaying another change

Resolves #49
improve display of comments formatted with wiki-like syntax

- use same converting code as used in web UI (GWT safehtml)
add message preview to review comment dialog
update changelog
Merge remote-tracking branch 'origin/master' into intellij13