Preparing for v1.0.0 release

[bennothommo]

What started off as adding support for relevancy and grouped results in the Docs plugin has become an all-encompassing push to get this plugin to v1.0.0 finally.

Changes

• Added support for grouped results, result relevancy and result labelling when using the Search plugin.
• Added support for linking PHP classes/interfaces/traits to the classes that extend/implement/use them in API docs.
• Added support for visibility label for properties and methods in the PHP API doc page table of contents.

Bug fixes

• Fixed memory issues and improved indexing of docs pages by using generators.
• Fixed delay when searching docs pages due to reindexing of the doc index on every search. The doc index will now only be indexed when run through the docs:process command.