Stabilization of Frontend build

I've repeated the Travis build [1] with this setup 50-times and 50-times it succeeded.

It means it is pretty stable. But in Bower case... who knows. :-)

[1] https://travis-ci.org/lfryc/aerogear-unifiedpush-server/builds/33060048I've repeated the Travis build [1] with this setup 50-times and 50-times it succeeded.

It means it is pretty stable. But in Bower case... who knows. :-)

[1] https://travis-ci.org/lfryc/aerogear-unifiedpush-server/builds/33060048

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Btw, the `admin-ui/` build is no longer the slowest part of the build!

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https://issues.jboss.org/browse/AGPUSH-955
Upgrade frontend tools to up to date versions

https://issues.jboss.org/browse/AGPUSH-938
Inspect AdminUI Grunt build to see whether we can trash use of some plugins

https://issues.jboss.org/browse/AGPUSH-873
UPS Admin UI: build fails with NPM > 1.4.9

https://issues.jboss.org/browse/AGPUSH-864
Leverage local NPM cache to avoid conflicts
yea, I believe so