Pixel digitizer cleanup 

Minor changes in pixel digitizer, for details see below:

In pixelDigitizer_cfi.py:

1) The variable “useDB”  is set to true. It should be set to false, it is related to a feature which has access to the whole gain calibration DB payload to search for dead-pixels. This has never been implemented and there are no dead pixels in the gain payload.
line: 50

2) We don't need the variable "AddPixelInefficiency". There is "AddPixelInefficiencyFromPython" instead. 
line: 45

3) Redundant commented variables.
line: 54-55    

In SiPixelDigitizerAlgorithm.cc:

4) There are several places where the first line in a method (e.g. pixel_inefficiency_db) is

if(!...) return

This is unnecessary. The value of this parameter is already known before calling the relevant method.
line: 1712, 1737, 1781

5) In DriftDirection() method the formula to compute the dir_z and scale are the same. We should not calculate it twice.
e.g. line: 1668

6) In PixelEfficiencies struct we don't need the "if (!...)" block. Variables in this block are used only when "AddPixelInefficiencyFromPython" is true.
from line: 442

7) Classes PixelBarrelName and PixelEndcapName are not used anymore.
line: 90-91

8) In PixelAging struct we don't need the "else" block. Variables in this block are used only when AddPixelAging is true.
from line: 488

9) Some additional corrections of annoying bad indents