Extend Link Checker code for storing more details

In order to provide the user with more details about the Link Checker
results, instead of storing whether the request was successful or not
I am not storing the response code, whether it timed out, etc.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Require Sidekiq debug environment per command line

It has become too cumbersome to comment in, comment out the require
statement in order to make the Sidekiq code debugable. Hence, I am
using this change to launch the debug environment per command line.

Now I can start the Rails server with the Sidekiq inline code by
an environment variable like so:

$ DEBUG=1 rails server

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Create controller and view for link checker report

I have decided to call to rename the metric detail views to metric
reports, like one would say report card. I have created a controller
parent class for the metric report controller. Also added a new method
to scroll through all the metadata which is not implemented yet.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Persist the Link Checker metric responses

Although I have already implemented storing the request responses I have
forgotten to add the specific variable so it becomes persistent.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Display URLs and their request responses

Added the code to list the URLs and their request responses in a table.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Style Link Checker report page

Just added similar styling to the Link Checker report page as on the
Completeness report page.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>