Sre v4 Integration

[zorkow]

Integration of new SRE v4. Depends on SRE v4.0.4.

Changes to SRE integration

SRE can now be imported directly via the file given in its distribution. To keep import clean sre.ts now imports all API methods and exports them for use elsewhere. Consequently modules depending on SRE only have to import sre.js. Files with old type handling (d.ts files) are removed.

Changes to the explorer

Most changes are wrt. the new handling of API methods and updating to new locales. The most significant change in logic is that setupEngine now returns a promise itself, indicating when locale loading has been complete. Consequently previously awkward constructions with sreReady are rewritten in explorer.ts but also in semantic-enrich.ts.

Changes to the components

The component integrating SRE is now build similar to other components:

• New sre component directory takes care the webpacking. Main file sre.js and configuration in sre_config.js
• No more need to distinguish between sre-node and sre-browser.
• Affects components depending on sre: semantic-enrich and a11y
• The PR also contains the new init.js component subsuming the startup.js calls implemented by @dpvc

New component

The PR also includes a new exemplary component tex-chtml-full-speech that demonstrates how SRE locales can be included via json imports in a MathJax distribution. This ensures that MathJax's internal MathMaps map is usually empty, keeping builds small and also allowing our lab still to work as usual.

[dpvc]

This looks good, but I think there is an issue with the promise handling in KeyExplorer. See the discussion in the comments to the code.

[zorkow]

Incorporates review suggestions. PTAL.

Note, that this also takes care of the path issue that I had mentioned yesterday. So no need for another PR on this.

However, I noticed that when a non-existent locale is provided in the option settings, we get a discrepancy in the context menu.
SRE will default correctly to English, but the menu will not show this. I will solve this in another PR.

[dpvc]

Two small changes requested, but otherwise looks good.