Remove old examples that require calbacks

[odow]

These examples are old, require commercial solvers, and use the callback functionality that has been removed in JuMP-0.19.

They still exist in the 0.18 branch so can be easily revived if/when callbacks are re-introduced.

Closes #1689

[codecov]

Codecov Report

Merging #1697 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1697   +/-   ##
=======================================
  Coverage   68.52%   68.52%           
=======================================
  Files          30       30           
  Lines        3867     3867           
=======================================
  Hits         2650     2650           
  Misses       1217     1217

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[codecov]

Codecov Report

Merging #1697 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1697   +/-   ##
=======================================
  Coverage   68.52%   68.52%           
=======================================
  Files          30       30           
  Lines        3867     3867           
=======================================
  Hits         2650     2650           
  Misses       1217     1217

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d32fce7...8deb447. Read the comment docs.

[IainNZ]

RIP that tsp code, I remember setting it up behind HttpServer.jl do demonstrate "TSP as a service"!