Category improvements

[jonchardy]

This PR makes a handful of changes based on requests and feedback from #866 and #904. I've also made a PR over at TypeStrong/typedoc-default-themes#61 to make categories more integrated into the theme.

Thanks to @rbuckton for the suggestions. I used some of the ideas from your implementation in your custom plugin.

Group Categories
Categories can now be used within groups or as lump categories. Lump categories mean if you have a method and property you want together, you can do so. The option --categorizeByGroup controls this. By default, reflections will be categorized by group (within properties, methods, etc).

Default Category
Uncategorized reflections will be placed in the default category. If everything falls into the default category, categories aren't used. The option --defaultCategory controls this. By default, the default category will be 'Other'.

Category Ordering
Categories can be ordered however the user wants. Using an array, the user can specify the order categories are displayed on their pages. The option --categoryOrder controls this. By default, they will be ordered alphabetically. An entry of '*' indicates where categories not in this list will be rendered, defaulting to the end.

[Gerrit0]

For the most part this looks awesome! Since it looks like the .toObject code has changed, could you update the reflection group serializer as well? We should be moving away from .toObject with #936

[jonchardy]

Made some updates for serialization. There will need to be more once this and #936 are merged, like updating the serialization schema. I only made changes based on the current serialization implementation.

[Gerrit0]

This looks good to me. Since it needs to be synchronized with TypeStrong/typedoc-default-themes#61 I think I'll leave the merge to @aciccarello

[BenDevelopment]

Hi,

When will this merge be released?