[front-end] add the button of a new page addition
[front-end] add  window for a new page addition
[front-end] implement new page addition
[front-end] change path to templateHTML
[front-end] put templates in separate dirs
[front-end] create templates.json, which holds list of all templates with descriptions and holders
[front-end] move templates into separate dirs
[build] copy templates.json and every template image to corresponding dir
[front-end] improve page addition controller
[front-end] add styles for page addition view
[front-end] improve page addition dialog
[front-end] dummy icons for widgets
[front-end] fix label placement
[front-end, refactor] use 2 spaces instead of 4
Merge branch 'develop' of https://github.com/sochka/wdc into iss82-new-pages-addition

Conflicts:
	src/main/webapp/WEB-INF/js/app.js
	src/main/webapp/WEB-INF/less/main.less