Remove scary warning

Removed scary warning that only applies to a single point release.

WIP: Add testing documentation

Two recent SE questions have made me think that readers are missing this
key set of installing CiviCRM with civibuild (instead of with the normal
installation steps). I've added clarification here which I hope will
prevent future users from stumbling on this step.

ref:

https://civicrm.stackexchange.com/questions/19294/how-to-create-entity-in-civicrm
https://civicrm.stackexchange.com/questions/19194/unable-to-locate-folder-xml-under-the-civicrm-root-directory

- Now includes for hook_civicrm_inboundSMS

CRM-20238 - Add documentation for hook_civicrm_inboundSMS

Update inboundSMS Documenation as per updated CiviCRM Core PR #10347

Python script for hooks summary

Basics: File System -- Add section on composer, bower, packages

Autogenerate hooks summary (with Symfony CLI tool)

Done with:
./bin/tools generate:hook-list

- Keep the summary short
- Use a separate "Notes" section for overflow

This way MkDocs will be able to report errors for broken links

Done with:

perl -0777 -i -pe \
's@(?<!!)\[([^\]]*)\]\((?!https?://)(?!mailto:)(/(?:(?:(?:/(?![\)#]))|[^/)#])(?!.md))+)/?(#[^)]*)?\)@[$1]($2.md$3)@gm' \
`find . -name '*.md'`

Previously this was necessary to get syntax highlighting to work, but
now just doing ```php will work.

Move them into the dedicated page on PhpStorm. Why? Tim has expressed
some concern about the potential difficulty (and slippery slope) of
starting to maintain IDE-specific docs. I like the PhpStorm page, but I
can see where he's coming from to a certain extent. As such, I think it
will be a good compromise if we can keep all the IDE-specific stuff as
consolidated as possible.

ref:
https://docs.civicrm.org/dev/en/latest/documentation/style-guide/#parts-chapters-sections