fix(firefox meta): in overlay.xul remove old DOCTYPE
feat(firefox meta): generate with gulp (insert project name)
refactor(build): generate builds/firefox from source/meta/firefox

Completely remove builds/firefox.
Clean it before generation, then use source/meta/firefox to fill it.
Add copyright notice to *.js files.
Use *.template.* files as templates (rename them to *.* before
writing to build/firefox).
Copy LICENSE.md from project root.
style(build): in gulpfile.js fix indentation
refactor(build): completely remove builds/, generate it all

- move everything from builds/ to source/meta/
- move .bat and .exe files to project root
- in gulpfile.js compile *.template.* files as Lo-Dash templates
- do not copy *.ignore.* files
- add copyright notice to *.js files

Also:
- turn chromium locale files into templates
- remove "appName" from them as it is not used
- rename builds/ to build/
- ignore build/

This closes #54, closes #55, and is related to #52 and #43.