[ClassMapGenerator] Refine the findClasses method

The code could not throw
[ClassMapGenerator] Improve error message when the path does not exist

i.e. the composer.json has a typo
[ClassMapGeneratot] Filter out non php code

Otherwise files like https://github.com/propelorm/Propel/blob/master/generator/lib/behavior/i18n/templates/queryUseI18nQuery.php
would fail ("class" keyword would not be filtered out by php_strip_whitespace())
Merge remote-tracking branch 'vicb/classmap'
Restore early return to happen as early as possible
Fix parsing of large files that go over the PCRE limits
Fix config listing
Fix handling of arrays in json manipulator
Allow the config command to read out values if no new value is provided
Remove target dir for classmap autoloads of the root package, fixes #1308
Add support for ~/+ in addition to - as separator between PHP version and build details, fixes #1322
Added addLink and removeLink to Configuration Source Interface

 * Added addLink() and removeLink() to `ConfigSourceInterface`
 * Added addLink() and removeLink() implementations to `JsonConfigSource`
 * Added tests (+ a ton of fixtures) for `JsonConfigSource`
 * Added additional docblocks
 * Minor PSR-1/PSR-2 fixes here and there
Merge pull request #1327 from simensen/config-add-remove-link

Added addLink and removeLink to Configuration Source Interface
Pass the current dev mode to the event dispatcher, which in turn passes it to the events fired. This can be fetched in scripts to check which mode we are currently in
Downgrade severity of branch-alias validation failure to warning
Merge remote-tracking branch 'christeredvartsen/script-dev-aware'
Fallback to PHP early if proc_open not allowed.
Remove reliance on proc_open in Filesystem#rename()
Skip locking dev package to time when proc_open does not exist on system.
Works on Linux when proc_open misses