Documentation link fix

While i was doing a new install, i realised that all link on the default pages were broken.
This is an attempt at fixing it.

I replaced the link to their equivalent on the manual.
So far the version is hardcoded to 1.1, that might need to be change in the long run.
I also replaced the "wiki" link at the bottom of the page by "manual" as i think the wiki is to be deprecated.

Also i just updated the following with the new URL to the "issues" page :
  * app/models/orchestration/dhcp.rb
  * app/views/common/500.rhtml

Also spotted few places where URL could do with an update:
```
extras/cli/foremancli:puts "     http://theforeman.org/projects/foreman/wiki/Search_API"
extras/cli/foremancli:opts.on( "--custom COLLECTION", "Custom COLLECTION string, see: http://theforeman.org/projects/foreman/wiki/API" ) do |f|
extras/foreman-release.spec:URL: http://theforeman.org/projects/foreman/
```

This was based on branch 1.1 .