Theming support

[damyanpetev]

• [ ] Add iOS and bootstrap themes (latter strings be like bootstrap3/default)
• [ ] Unify theme choices across projects

As there are structure changes in 17.2, some parts of this might need to wait for the new package and #64.

Custom themes: Currently only the jQuery project has a semi-functional solution that'll bring the selected theme files(less source incl.) into the project structure and set it in the config. I think it still need a structure update to provide an additional file that @imports the theme to allow for easy overrides. That also means a build task should run less/sass if needed.

• [ ] Finish jQuery implementation - per above, plus properly apply themePath to templates
• [ ] React implementation
• [ ] Angular implementation