General insertion interface for datatypes

*Title: General insertion interface for datatypes

Incentive:
Make it easier to inserts files, text and complex xml into any datatype trough a common interface.
This will reduce code involved and remove a lot of the internal variable handling to the given
datatype. It will also simplify future updates of Exponential.


*Documentation:
Some new methods are introduced to the eZDatatype interface, there are one method
for querying for a special insert type and one for doing the actual insertions.

isxxxInsertionSupported(): Returns true if supported or false if not, default for all datatypes is false
insertxxx(): Tries to insert the type, returns true on success, false on failure or null if not supported.


Insertion types:
HTTP file: This is a file that is uploaded by the user using the web interface

methods:
 - isHTTPFileInsertionSupported(): Returns true if the datatype supports this
 - insertHTTPFile(): Inserts the specified HTTP file

datatypes:
 - ezimage: Stores as image
 - ezbinaryfile: Stores as binaryfile
 - ezmedia: Stores as media file


Insertion types:
Regular file: This is a file that exists on the system

methods:
 - isRegularFileInsertionSupported(): Returns true if the datatype supports this
 - insertRegularFile(): Inserts the specified file

datatypes:
none yet

Insertion types:
Simple string: A simple string on one or multiple lines.

methods:
 - isSimpleStringInsertionSupported(): Returns true if the datatype supports this
 - insertSimpleString(): Inserts the string

datatypes:
 - ezstring: Stored as data_text
 - eztext: Stored as data_text

*Testing:

*SVN Revisions:
7425