Few czech translation strings added.

core/src/main/resources/hudson/util/HudsonIsLoading/index_cs.properties

+# This file is under the MIT License by authors
+
+Please\ wait\ while\ Jenkins\ is\ getting\ ready\ to\ work=Po\u010Dkejte pros\u00EDm, ne\u017E aplikace Jenkins zcela nab\u011Bhne
+Your\ browser\ will\ reload\ automatically\ when\ Jenkins\ is\ ready.=Jakmile bude Jenkins p\u0159ipraven, str\u00E1nka se automaticky obnov\u00ED.

core/src/main/resources/jenkins/diagnostics/SecurityIsOffMonitor/message_cs.properties

+# This file is under the MIT License by authors
+
+Setup\ Security=Nastaven\u00ED zabezpe\u010Den\u00ED
+Dismiss=Rozum\u00EDm
+blurb=Nezabezpe\u010Den\u00FD b\u011Bh aplikace Jenkins umo\u017E\u0148uje komukoliv na s\u00EDti spou\u0161t\u011Bt procesy va\u0161\u00EDm \
+  jm\u00E9nem. Pro omezen\u00ED tohoto zneu\u017Eit\u00ED pros\u00EDm zva\u017Ete zapnut\u00ED autentizace do aplikace Jenkins.