Bugfix/security vulnerabilities

[wblachowski]

Fixes security vulnerabilities reported by GitHub.

Description

Closes #407

Motivation and Context

Reported vulnerabilities in AET 3.2.0:

Most of these come from bower, which is deprecated for over a year now so no chances of it getting patched. For this reason I ditched bower altogether replacing it with npm for downloading dependencies + gulp-npm-copy-deps for copying them to the assets directory,

Apart from bower, gulp-sass, browserify and commons-fileupload had to be updated.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• I have reviewed (and updated if needed) the documentation regarding this change

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I hereby agree to the terms of the AET Contributor License Agreement.

[bambroziak]

Tested and accepted:
Changes did not couse any error, AET build correctly and does not show any unexpected results.
Code were also covered and works fine.

QA Approve.