Add new API object VotingRangeInfo to represent continuous voting range
from min to max values.
Add VotingRangeInfo as field to ApprovalInfo, the new
field represents the range of values the approver is permitted
to vote on the label.
Updated reviewers UI tooltip to indicate the reviewers
who have maximum vote permission on the label. For example
the tooltip will show "Votable: Code-Review (+2)" if the
reviewer is permitted to vote with maximum range value for
Code-Review label. If the reviewer isn't permitted to vote
with maximum range value, but still votable for Code-Review
label the "Votable: Code-Review" will be shown.
This change will allow authors to easily verify (by API and UI)
reviewers with +2 Code-Review permission assigned for the change.
Change-Id: I47e692b82691b87eefbc2143e10b99bcf49c1d29
bf313bbbba