Use well to name mapping when copying the old well state to the new
With the introduction of shut wells the same ordering in the well states
can no longer be assumed. The well names is instead used to map the old
well state to the new. Also the partial_copying is moved into the
initialization.

Tested on SPE1, SPE3, SPE9 and Norne. (Do not change the SPEs and is
nessesary for the Norne)
Adressing comments in the PR
The following comments has been adressed
1. An array is used in stead of pair
2. is not empty is used instead of size>0 to check if the well has been
initialized before
3. const_iterator is used instead of iterator
4. partial copy is removed
5. WellMapType is no longer mutable
Merge pull request #228 from totto82/partial_copy2

Use well to name mapping when copying the old well state to the new