hgweb: handle a "linerange" request parameter in filelog command
We now handle a "linerange" URL query parameter to filter filelog using
a logic similar to followlines() revset.
The URL syntax is: log/<rev>/<file>?linerange=<fromline>:<toline>
As a result, filelog entries only consists of revision changing specified
line range.
The linerange information is propagated to "more"/"less" navigation links but
not to numeric navigation links as this would apparently require a dedicated
"revnav" class.
Only update the "paper" template in this patch.