Minor improvements for encoder configuration, LCD entry for PSU controll and thermistor pins on RAMPS

Commit  b7eadb9
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After wiring my RepRap with RAMPS I discovered that thermistor pins are not subsequential ordered.

For your reference RAMPS Pins:
http://reprap.org/mediawiki/images/c/ca/Arduinomega1-4connectors.png

**Example:**
Using one extruder and a heated bed, connections have to be

* D8 Heated Bed
* D9 ---
* D10 Extruder
* T0 Extruder
* T1 Heated Bed
* T2 ---

For the sake of logic it should be

* D8 Heated Bed
* D9 ---
* D10 Extruder
* T0 Extruder
* T1 ---
* T2 Heated Bed

**As this breaks wiring for many people so this change should be postponed till next major version.**


Commit  e5d3044
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When using a highres encoder it's possible to change *ENCODER_PULSES_PER_STEP* in *Configuration.h* but not *ENCODER_STEPS_PER_MENU_ITEM* leaving the user with a strange experience while navigating throught the menu. I added an #ifndef in *ultralcd.cpp* so it's possible to overwrite this setting in *Configuration.h*.


Commit 20faff5
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When setting *PS_DEFAULT_OFF*, PSU is off when booting but the LCD menu entry offers to turn PSU off, as the routine doesn't check for *PS_DEFAULT_OFF*. I changed that so the menu entry equates reality.


**Additionally, I cleaned some trailing white spaces**