Add verbosity to VersionTask

[jawira]

Using VersionTask is not so obvious at the beginning, so I added some log messages. I also did a small code refactoring.

[siad007]

@jawira Thanks for your PR but there is at least one failing test. Would you mind have a look at
/home/travis/build/phingofficial/phing/test/build.xml:80:25 Test FAILURE (testPropFileWithDefaultProperty in class VersionTaskTest): property build.version
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'4.5.5'
+'0.0.1'

[codecov]

Codecov Report

Merging #967 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #967      +/-   ##
============================================
- Coverage     44.88%   44.87%   -0.02%     
  Complexity     9921     9921              
============================================
  Files           499      499              
  Lines         24046    24049       +3     
============================================
- Hits          10793    10791       -2     
- Misses        13253    13258       +5

Impacted Files	Coverage Δ	Complexity Δ
classes/phing/tasks/ext/VersionTask.php	79.06% <100%> (+0.75%)	27 <3> (ø)	⬇️
classes/phing/util/SourceFileScanner.php	63.76% <0%> (-7.25%)	21% <0%> (ø)

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[jawira]

Yep, I fixed the bug :)