Globally configured redmine websites

Hi,

This pull request rework way, how redmine websites are defined and assigned to project. Now you can globally configure redmine websites and in project configuration page you can refer configured ones. I've also added new redmine logo to redmine link action.

Some notes:
- I'm having issues with developing plugin when in pom.xml there is dependency:

      	<groupId>org.jvnet.hudson.plugins</groupId>
      	<artifactId>subversion</artifactId>
      	<version>2.0.1</version>
but when i use following dependency there is no problem:

      	<groupId>org.jenkins-ci.plugins</groupId>
      	<artifactId>subversion</artifactId>
      	<version>1.45</version>
- I don't know how handle situation, when user remove global redmine website config but project has still assigned old one.