Add configuration option for the frequency that branches are checked remotely

[lapo-luchini]

Would close #126 to me.

[JohnstonCode]

Thanks for this

[codecov]

Codecov Report

Merging #130 into master will increase coverage by 0.19%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master     #130      +/-   ##
==========================================
+ Coverage   40.72%   40.91%   +0.19%     
==========================================
  Files          17       17              
  Lines        1434     1437       +3     
  Branches      223      224       +1     
==========================================
+ Hits          584      588       +4     
+ Misses        848      847       -1     
  Partials        2        2

Impacted Files	Coverage Δ
src/repository.ts	60.73% <80%> (+0.62%)	⬆️
src/svnRepository.ts	66.04% <0%> (+0.61%)	⬆️

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