add support for managing initialization parameters
fix last part of renaming this type from 'parameter' to less confusing 'init_param'
always just write to spfile for now. ToDo: fix this properly
add basic unit tests
add more unit tests (copied from tablespace_spec mostly)
add more basic unit tests for value parameter
cleanup stubs of spfile/modifiable code which was not really working yet anyway
Merge pull request #11 from bjoernrost/master

basic support for initialization parameters