[Widgets] Tooltip word wrap fixup

QTooltip's documentation states that "rich text displayed in a
tool tip is implicitly word-wrapped". This seems to be a more
desirable behavior for our needs.
To mitigate any potential malicious tooltip contents, we escape
any eventual html entities, and truncate to a reasonable size.

Change-Id: Iae3ea80e7660840aae39d228d1177dcc56f4a032
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>