#40 Several bugs found when testing CWM generation

[Niko]

Generator:
* Complex db_data_types containing single quotes (e. g. ENUM) lead to error in RDBMapper and DBUpdate
* Display error if required properties of WCMFActionKey (action and config) are not set
* Display error if two Controllers use the same action
* Check if a class has WCMFValue as (in)direct Superclass
* Make errors more visible

Framework:
* An object able to have its own type as child displays its own name in the list rather than the child's name

Installation:
* Check if a table or column really exists prior to executing ALTER statement
* Check if a table or column really doesn't exist prior to executing CREATE statement
* Make errors more visible

[ingo herwig]

* add a generator check that ensures that roles are set at _all_ ends of multiple associations or define default rolenames if not