Improve duplicate resolving

[koppor]

Idea: For duplicate bibtex keys, there should be the possibility to open the merge entries dialog

@Article{CST+2010,
  Title                    = {Benchmarking Cloud Serving Systems with YCSB},
  Author                   = {Cooper, Brian F. and Silberstein, Adam and Tam, Erwin and Ramakrishnan, Raghu and Sears, Russell},
  Year                     = {2010},
  Doi                      = {10.1145/1807128.1807152},
  Pages                    = {143--154},
  Series                   = {SoCC '10},

  Acmid                    = {1807152},
  Address                  = {New York, NY, USA},
  Booktitle                = {Proceedings of the 1\textsuperscript{st} ACM Symposium on Cloud Computing},
  File                     = {:CST+2010 - Benchmarking Cloud Serving Systems with YCSB.pdf:PDF},
  ISBN                     = {978-1-4503-0036-0},
  Journal                  = {Proceedings of the 1st ACM Symposium on Cloud Computing},
  Keywords                 = {benchmarking, cloud serving database},
  Location                 = {Indianapolis, Indiana, USA},
  Numpages                 = {12},
  Owner                    = {andreas},
  Publisher                = {ACM},
  Timestamp                = {2015.09.15}
}

and

@InProceedings{CST+2010,
  author    = {Cooper, Brian F. and Silberstein, Adam and Tam, Erwin and Ramakrishnan, Raghu and Sears, Russell},
  title     = {{Benchmarking Cloud Serving Systems with YCSB}},
  booktitle = {Proceedings of the 1\textsuperscript{st} ACM Symposium on Cloud Computing},
  year      = {2010},
  publisher = {ACM},
  acmid     = {1807152},
  file      = {:CST+2010 - Benchmarking Cloud Serving Systems with YCSB.pdf:PDF},
  isbn      = {978-1-4503-0036-0},
  keywords  = {benchmarking, cloud serving database},
  location  = {Indianapolis, Indiana, USA},
  numpages  = {12},
  owner     = {andreas},
  timestamp = {2015.09.15},
}