Implementing soft delete

Soft delete can now be activated for reader and writer in Berthe.
What is needed is the name of the column associated with the softdelete.
If this is not specified, a normal delete will be performed.
Now auto filtering (a.k.a soft delete filtering) is done using fetchers.

Also adding proper phpdoc
Remove unecessary curly bracket
Add the possibility to specify the filtered value of the auto filtered column in abstractReader
Add type checking
Change softdelete value from true to 1

(this allows the soft delete to work as well for column of type smallint)
'Remove wrong typehint in setSoftDelete function'
Add proper namespace for InvalidArgumentExpression
Merge pull request #33 from Evaneos/soft-delete

Implementing soft delete