doc: tweaks to CONTRIBUTING.md

- subheads so we can link directly to CONTRIBUTING.md#cask-stanzas
- clarification on naming `pkg` Casks
- fix repetitive language
doc: drop version numbers from end of Cask names
Add docs for Caskfiles
Add dotfiles section to Caskfile docs
New cask: vassal 3.2.11
Update owncloud.rb

updated to version 1.5.2.2335
Merge pull request #3295 from phpwutz/patch-1

Update owncloud to 1.5.2.2335
Merge pull request #3293 from ndr-qef/doc-automation

Add docs for Caskfiles and automation
Merge pull request #3294 from res0nat0r/vassal-3.2.11

New cask: vassal 3.2.11
Merge pull request #3286 from rolandwalker/doc_contributing_tweaks

doc: tweaks to CONTRIBUTING.md
Merge pull request #3285 from rolandwalker/doc_cask_name_drop_version

doc: drop version numbers from end of Cask names
rename flash-decompiler.rb

to flash-decompiler-trillix.rb
per naming rules in CONTRIBUTING.md
rename fm-designer.rb

to b2designer.rb
per naming rules in CONTRIBUTING.md
rename repetier.rb

to repetier-host.rb
per naming rules in CONTRIBUTING.md
rename zap-proxy.rb

to owasp-zap.rb
per naming rules in CONTRIBUTING.md
rename gpower3.rb

to gpower.rb
per naming rules in CONTRIBUTING.md
rename marked2.rb

to marked.rb
per naming rules in CONTRIBUTING.md
rename airmail-beta.rb

to airmail.rb
per naming rules in CONTRIBUTING.md
Merge pull request #3300 from rolandwalker/rename_fm-designer

rename fm-designer.rb
Merge pull request #3299 from rolandwalker/rename_repetier

rename repetier.rb