Catch uncaught errors and display the error message on the page itself
if bootstraping fails. This should prevent most cases of the of the web
interface being stuck on "Loading web interface..." after an error was
thrown and the loading failed.
Clean up the configuration for compiling TypeScript for the Web
interface to us its own tsconfig.web.json config files and reference the
TypeScript source files directly in the configuration and imports
instead of files compiled to dist.
To properly support recompliation with TypeScript's projects feature
each package's tsconfig.web.json file is set to output the build to
dist/web_build which is then ignored in .npmignore. Webpack is still
used to create the proper build in dist/web, so this is mainly to make
TypeScipt's compiler happy but it also allows the root tsconfig.json
file to include the web interface code, meaning running the build script
now also checks the typing of the web interface.
Final part of #491.