Added dynamic insertion for TCK and TRK, and added default header per format.

It is not mandatory to provide an header when creating a new file.

Each file format now defines its own default-empty header that is use when creating
a new file.

iadd() of TCK and TRK will now update the number of streamlines contained in a file.
Updated version number
Added deepcopy of hdr when creating a new file. Now support 4D anatomy.
Removed dbg()