Format the possible version formats as a table

Note I: This syntax is supported by MarkdownExtra, which both getcomposer
and github are using.

Note II: This patch currently breaks the PDF, because pandoc does not like
non-standard markdown tables. Ideas for fixing this appreciated.

Note III: The idea for this patch came up a few weeks ago on IRC. We
agreed back then that a table would be a good idea.

Note IIII: This patch creates a stability section which opens the door for
finally documenting how stability works in the composer docs.
Document logical OR constraints
disable prepend option on install
disable prepend option on update
Add local cache for Git repositories
Add temp composer home for GitDriver test using cache
added warning about referencing dependencies in pre-install and pre-update
fix up markdown
fix line lengths
Fix for Preforce utility does not check if p4 command exists
Check for exit code is equal to 0 instead of 127
Changes comparsion to strict and removed a comment
Removed unnecessary test and just check for return code
refactor prepend autoloader from cli option to config var (prepend-autoloader) in composer.json
Add documentation for resolve-dependencies
Merge pull request #2302 from igorw/versions-table

Format the possible version formats as a table
Change dependency processing for update with whitelisted packages
By default dependencies of white listed packages are no longer installed automaticaly.
To Install dependencies of whitelisted packages use --with-dependencies.
- rework after review comments
- precise documentation of option
- add missing punctuation marks
non-deep check returns allways false
Merge remote-tracking branch 'fabiang/preforce'
Minor tweaks to perforce support, refs #2329