Performance improvement in Row

Performance improvement in Row

Various performance improvements to Row instanciation
- avoid passing processors if they are all None
- improve processor logic in cython
- improve tuplegetter using slices when contiguous indexes are used

Some timing follow.

In particular [base_]row_new_proc that tests using processors has
a 25% improvement compared to before in cython.
Looking at the [b]row_new_proc_none that test a list of processors
all None, this has 50% improvement in cython when passing the none list,
but in this patch it would usually be disabled by passing None, so the
performance gain is actually 90%, since it would run the case
[base_]row_new.

Tuplegetter is a bit faster in the single item get and when getting
sequential indexes (like indexes 1,2,3,4) at the cost of a bit
longer creation time in python, cython is mostly the same.

Current times
                    | python      | cython      | cy / py     |
base_row_new        | 0.639817400 | 0.118265500 | 0.184842582 |
row_new             | 0.680355100 | 0.129714600 | 0.190657202 |
base_row_new_proc   | 3.076538900 | 1.488428600 | 0.483799701 |
row_new_proc        | 3.119700100 | 1.532197500 | 0.491136151 |
brow_new_proc_none  | 1.917702300 | 0.475511500 | 0.247958977 |
row_new_proc_none   | 1.956253300 | 0.497803100 | 0.254467609 |

tuplegetter_one     | 0.152512600 | 0.148523900 | 0.973846751 |
tuplegetter_many    | 0.184394100 | 0.184511500 | 1.000636680 |
tuplegetter_seq     | 0.154832800 | 0.156270100 | 1.009282917 |
tuplegetter_new_one | 0.523730000 | 0.343402200 | 0.655685563 |
tuplegetter_new_many| 0.738924400 | 0.420961400 | 0.569694816 |
tuplegetter_new_seq | 1.062036900 | 0.495462000 | 0.466520514 |

Parent commit times
                    | python      | cython      | cy / py     |
base_row_new        | 0.643890800 | 0.113548300 | 0.176347138 |
row_new             | 0.674885900 | 0.124391800 | 0.184315304 |
base_row_new_proc   | 3.072020400 | 2.017367000 | 0.656690626 |
row_new_proc        | 3.109943400 | 2.048359400 | 0.658648450 |
brow_new_proc_none  | 1.967133700 | 1.006326000 | 0.511569702 |
row_new_proc_none   | 1.960814900 | 1.025217800 | 0.522852922 |

tuplegetter_one     | 0.197359900 | 0.205999000 | 1.043773330 |
tuplegetter_many    | 0.196575900 | 0.194888500 | 0.991416038 |
tuplegetter_seq     | 0.192723900 | 0.205635000 | 1.066992729 |
tuplegetter_new_one | 0.534644500 | 0.414311700 | 0.774929322 |
tuplegetter_new_many| 0.479376500 | 0.417448100 | 0.870814694 |
tuplegetter_new_seq | 0.481580200 | 0.412697900 | 0.856966088 |

Change-Id: I2ca1f49dca2beff625c283f1363c29c8ccc0c3f7