Make versionsLT support versions with qualifier (#307)

Extracted functions to jenkins-support; included in both jenkins.sh and
install-plugin.sh.

Added a separate test file to test versionLT function
diff --git a/install-plugins.sh b/install-plugins.sh
index 4e47afe..cdb2917 100755
--- a/install-plugins.sh
+++ b/install-plugins.sh
Binary files differ