Update frontend-maven-plugin from 1.4 to 1.6
<node.version>4.0.0</node.version>
<npm.version>2.13.1</npm.version>
<yarn.version>0.23.0</yarn.version>
- <frontend-version>1.4</frontend-version>
+ <frontend-version>1.6</frontend-version>
<skip.node.tests /> <!-- changed by -DskipTests, if specified - see profile -->
<skip.node.lint /> <!-- changed by -DskipLint, if specified - see profile -->
<npm.loglevel /> <!-- may use e.g. -\-silent (without backslash) -->
