Remove Old Manual Linking In Favor Of Autocrossref

* This change only removes brackets (and, in one case, adds two
  brackets). No other changes were made to the dev guide.

* A few terms I missed previously were added to _autocross.yaml.

* Links checked; all internal links link to valid ids except the link
  definitions including "FIXME". (See bottom of the file.)

* A few links were left in where they linked to terms I didn't think
  should be autocrossref'd
Merge remote-tracking branch 'saivann/dev' into finishxref

Conflicts:
	en/developer-guide.md
Add Short (400-Word) Introduction

* Describe the bare essentials to getting started plus how to use the
  guide's special features.

* I tweaked the noref regex to match any non-space character between the
  key and the noref tag, so we can easily prevent "terms" from being
  matched in strings like "terms-are-cool". For an example, see norefs
  next to `-testnet` strings in Intro section

* I didn't give the Introduction an h2 tag on purpose---I like jumping
  right in. However, I'm open to feedback.
Show crossref links on mobiles
Merge pull request #3 from saivann/devintro

Show crossref links on mobiles
Merge pull request #64 from harding/finishxref

Finish Implementing Auto Cross-References
Emphesize Advantages Of Regtest Mode (thanks @mikehearn!)
Merge branch 'intro' of https://github.com/harding/bitcoin.org into intro
Merge pull request #65 from harding/intro

Add Short (400-Word) Introduction
Updating Mining Section Based On Feedback From @instagibbs and @saivann

This is the "haste makes waste" update.  I should've known better than
to try to write the Mining section quickly.  :-)

Over 100 net lines were added, making the following changes:

* Changed introduction to define solo/pool miners by their goals rather
  than whether they're peers. Suggested by @instagibbs (thanks!)

* (No substantive changes to the solo mining text.)

* Removed extra ASICs from solo mining illustration.

* Generalized how pool miners get work to allow for different methods
  described later.

* Removed extra mining pool and ASICs from pool mining illustration.
  Changed "block template" (still used in solo illustration) to
  "prototype block". Based on feedback from @saivann and a specific
  suggestion by @instagibbs (thanks!)

* Give `getwork`, `getblocktemplate`, and Stratum each their own
  subsubsection describing them in overview-level detail using parallel
  structure for easy comparison.
Merge remote-tracking branch 'saivann/dev' into mining

Conflicts:
	en/developer-guide.md