Fixed Iroha container port

[dolgopolovwork]

New withFixedPort method that allows setting a fixed Iroha port.

[codecov-io]

Codecov Report

Merging #49 into master will decrease coverage by 0.27%.
The diff coverage is 14.28%.

@@             Coverage Diff              @@
##             master      #49      +/-   ##
============================================
- Coverage     73.01%   72.74%   -0.28%     
  Complexity      346      346              
============================================
  Files            38       38              
  Lines          1601     1607       +6     
  Branches         50       51       +1     
============================================
  Hits           1169     1169              
- Misses          350      355       +5     
- Partials         82       83       +1

Impacted Files	Coverage Δ	Complexity Δ
...soramitsu/iroha/testcontainers/IrohaContainer.java	77.9% <14.28%> (-5.85%)	19 <0> (ø)

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