Fix getAdapterConnection() to not always create a new connection

$adapterConnections is a class property not a local variable here
Removed all peer stuff.

Adjusted documentation, .xml etc.
Abstracted connection handling, so we don't deal with PDOStatement directly anymore, but with DataFetcher, which hides the adapter specific stuff. (PDOStatement etc.)
Abstracted OM build process, so the platform overwrite which OM Build class we use. (`getBuilderClass()`)
Made populateObjects name-indexed compatible.
Fixed typos
Merge pull request #366 from rlerdorf/patch-1

Fix getAdapterConnection() to not always create a new connection
Remove debug print calls. Fixes #207
Fix CS
[Generator] Add a short alias for each command from propel 1.6 command names
Merge pull request #370 from GromNaN/alias

Add a short alias for each command from propel 1.6 command names
Fixed 2 typos.
Fixed a bug where the MigrationDiffCommand can not find the buildtime config if the cwd is not equal to the directory of the buildtime file.