ID for HTML elements should be unique.
Added regression tests for HTML pages.
[FIXED JENKINS-23561] Copied matrix.jelly from Jenkins 1.509 (/lib/hudson/project/matrix.jelly).
[JENKINS-23561] Removed language-specific texts from taglib.
Applied the taglib also to value.groovy. Removed an unnecessary heading.
[JENKINS-23030] Added a test to reproduce JENKINS-23030.
[FIXED JENKINS-23030] Use Combination for Layouter instead of built-in Layouter. This avoids NPE when MatrixCombination is not available.
Merge pull request #7 from ikedam/feature/JENKINS-23561_UseOwnTaglib

[JENKINS-23561] [JENKINS-23030] Use customized matrix tag