[jdk8u-dev] RFR: 8176509: Use pandoc for converting build readme to html

[Zdenek Zambersky]

This backport switches to pandoc for coversion of building readme to html. It also does some style/formating changes/fixes to building readme, which is moved to new location and also removes redundant information in other Readme files.

Backport is not clear. Code for coversion to html had to be modified to work with JDK8 build system. Change set (patch) for building readme mostly applied automatically, but some parts had to be done by hand due to few differences.

Unlike in original change set, this backport moves `README-builds.{md,html}` files directly to `doc/building.{md,html}` and not to intermediate location `common/doc/building.{md,html}`. (additional move was done in jdk10 as part of [JDK-8187443](https://bugs.openjdk.org/browse/JDK-8187443))

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Commit messages:
 - Backport 9d0bd1b495012de5de1c62f65f14c4de36aef056

Changes: https://git.openjdk.org/jdk8u-dev/pull/370/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=370&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8176509
  Stats: 5004 lines in 16 files changed: 2140 ins; 2854 del; 10 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/370.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/370/head:pull/370

PR: https://git.openjdk.org/jdk8u-dev/pull/370