Automatically adjust web.forwardSlash on Tomcat containers

One issue that frequently arises in the discussion group and the bug
tracker is how Tomcat automatically re-encodes %2f as '/' which breaks
url parameters with %2f.  After documenting this in half a dozen places
it still comes up.  Clearly I haven't done enough.

Gitblit will now act on, instead of just report, an improperly configured
web.forwardSlash character on Tomcat containers.  This will make Gitblit
"just work" for more users and will make the world a better place.

Change-Id: I344428804070a2d6082022cf6b80e2a3d83cea84