Clean up and refactor codebase

[dymurray]

• There are many instances of duplicated code across backup/restore in the same package that can be cleaned up. An example:
  https://github.com/fusor/ocp-velero-plugin/blob/master/velero-plugins/common/backup.go#L49
  https://github.com/fusor/ocp-velero-plugin/blob/master/velero-plugins/common/restore.go#L49

• A lot of backup code is doing nothing... would be good to go through and delete whatever we are not using:
  https://github.com/fusor/ocp-velero-plugin/blob/master/velero-plugins/route/backup.go
  https://github.com/fusor/ocp-velero-plugin/blob/master/velero-plugins/buildconfig/backup.go

• Remove all copyrights that refer to heptio's contributors

[alexander-demicev]

I will take this issue

[alexander-demicev]

#12 - Removed copyrights

[alexander-demicev]

#19 - Removed unused code

[alexander-demicev]

#23