Fix HTMLText AbsoluteLinks not parsing placeholder

Add an AbsoluteLinks method to HTMLText that parses placeholders instead of returning the raw value.
Upload: refactor file versioning
Fix: Incorrect calculation of UploadField height (fixes #2862)
Fix: Remove superfluous iframe resize for UploadField (fixes #2863)
ENH making /dev extendable
BUG Fixing plural_name messing up singular words ending in "e" (#3251)

This would ideally be fixed with the ability to use an external library
like gettext, but that's an API change. This for now fixes the issue
where a singular like "Page" returns "Pags" for the plural name.
BUG Fix issue with inheritance of Injector service configuration
Copy SSViewer rewrite_hash_links regexp to SSTemplateParser
As this is meant to represent the same functionality in two different
areas, it should behave the same way in both.
Update PhpUnitWrapper.php & TestRunner.php to recommend PHPUnit installation via Composer rather than PEAR

Using the PEAR Installer to install PHPUnit is no longer supported.  See https://github.com/sebastianbergmann/phpunit/wiki/End-of-Life-for-PEAR-Installation-Method.

Replace PEAR in a comment and die output message with Composer.

Signed-off-by: AntonyThorpe <antony.thorpe@budget12.com>
Merge pull request #3476 from AntonyThorpe/PEAR-PHPUnit

Update PhpUnitWrapper.php & TestRunner.php to recommend PHPUnit installation via Composer
Adding some README badges for downloads, license and stable version.
Fixing broken docs on setting allowed extensions on a FileField

Refers to an invalid variable, and is overriding the entire Upload,
which isn't necessary.
Merge pull request #3478 from halkyon/readme_badges

Adding some README badges for downloads, license and stable version.
Merge pull request #3480 from halkyon/allowed_exts_doc_change

Fixing broken docs on setting allowed extensions on a FileField
Fix #3356 js not properly included
Updated en/topics/testing/index.md for clearer PHPUnit installation instructions

Step by step Composer installation instructions, including a composer.json example.

In addition:
- Removed self-page reference to an introduction
- Removed reference to PEAR installation instructions due to end of life
- Removed reference to Ruby as doesn't add value
- Shortened testing via Web Browser section (as covered in Composer installation instructions)
Update 5-dataobject-relationship-management.md

Fixed two small mistakes:

"select one the the mentors" -> "select one of the mentors"
WYSIWIG -> WYSIWYG
Merge pull request #3485 from dpenas/patch-1

Update 5-dataobject-relationship-management.md
Updated html field to support quotes
Describe adding PHPUnit as a simple one line command

- Removed the composer.json example
- Removed comment about PHPUnit versions

Signed-off-by: AntonyThorpe <antony.thorpe@budget12.com>