[FEATURE] Files::removeEmptyDirectoriesOnPath()

This change introduces a new utility function which removes all
empty directories on a given path.

Change-Id: I1f495f7aee3550d4c8a3631adc9f8fc276f3da6c
Releases: master
[BUGFIX] buildSubprocessCommand fails with multiple arguments

Fixes an issue where the buildSubprocessCommand() function returned
an invalid command line which lacked spaces between command options.

Change-Id: I5d309c4a3cdc7b6db13c4fafaa0e9c3f6e34dc3b
Resolves: #49503
Releases: master, 2.0
[TASK] Clean up tests and fix for PHPUnit 3.8

Change-Id: Ic26d7a2b2c7dda05a9c868f6539787ed4dae240e
Releases: master, 2.0