Make create_directory fail with API_E_ALREADY_EXISTS if the directory already exists
Rename program name to program identifier

To emphasis that this is not the display name for the program configuration
but an identifier for it. Because this identifiert will be used as directory
name it has a resricted alpahabet.
Replace with_internal_reference of object_create function with flags parameter
Adapt more variable names to the common naming pattern
Fix length check afor redapid directory name
Don't abuse the internal reference count as program defined state indicator
Rename API_E_OBJECT_IS_LOCKED to API_E_OBJECT_IN_USE
Allow to create initially occupied objects

With this the pipe wrappedin a file object can have a normal name
string object.
Create program directory in define_program function
Add get_program_directory function to program object API