subroutines for additional url parameter "repo_id"

if a specific repository id is passed in url parameter "repo_id", then
try to find it in the list of current project repositories and use only
this and not all to pull changes from (fixes issue #54)
Logging info for which repos have been updated
indent other log messages
add profiling/debug info in log about how long the fetch and redmine import commands have taken
 updated README.md to reflect new plugin behavior
Merge pull request #58 from tofi86/feature/update-repo-from-url-param

Feature/update repo from url param