* Fix tsconfig scopes affecting html.js
Since it's quite hard to use a DOM library type there, remove the type
entirely.
* Remove environment variables check
Nothing is using them anymore. It can be added back if needed later.
* Refactor Texture Packer downloading
Refactor local-config.js tasks file into a generic "environment"
category consisting of checking if Java is installed, downloading the
runnable Texture Packer if it's not yet downloaded and copying the local
configuration template; update README accordingly.
* Prepare environment only at postinstall
Remove environment.prepare task from default build pipelines, add a
postinstall script that calls the task, using environment.js as the
gulpfile to speed it up.
* Remove "docs" tasks and types generation script
Remove tasks from docs.js as they are unlikely to do anything meaningful
nowadays. Also remove the buildTypes script as it doesn't work anymore.
A better solution will be provided in the future.
* Simplify some globs
Use additional gulp.src options instead of specifying more or complex
globs.
* Extract built-temp location to a variable
Add the src/js/built-temp directory as a new variable in config.js,
replace all existing references to built-temp with this variable.
