make release date optional as defined in schema.
Merge pull request #31 from Discordier/make-optional

make release date optional as defined in schema.
Add legacy repository to default composer.json.
Implement database update.
make release date comparison optional and not raise a fatal exception.
keep track of already seen versions when fetching from multiple repositories
to ensure each version is only mentioned once. Before, the installed version
was mentioned twice, as it originated from the local repository and the
remote one.
url decode version to allow ">=" and "<=" being used again in contao context.
also show the installation source for installed condidates.
Rework backend listing, hide dependencies by default. Implements #39
Replace "to long" type labels with icons.
Add icon for component packages.
Replace icon with a label if there is no icon for the package type available.
Set env COMPOSER_HOME if neither HOME or COMPOSER_HOME are set.

Fixes #38
Redirect back to package list, if update fail.
Fix optical "oversize" of the output element.
Add dependency graph view. Fixes #40
Adding myself as developer and reindenting the composer.json at the same time.
Merge branch 'master' of github.com:ContaoCommunityAlliance/Composer
Merge pull request #42 from discordier/master

Adds myself as author to composer.json and reindents it properly
Remove composer-installer as dependency from global composer.json.